Dear mum and dad, basically what I have to say is that I am extremely sorry that I had gotten my self in that situation and I can promise it will not happen again.
The drug that I had taken was called flubromazolam, this is a type of Benzodiazepine, Benzodiazepines are a type of medication known as tranquilizers. Familiar names include Valium and Xanax.
I am not trying to justify the use of drugs I am simply try to educate you because I feel without doing so it will damage our relations and make living together difficult, both you and dad have the view that doing drugs instantly puts you in a category of a "junkie" or a "waster" when in reality this is not true.
If this were to be true almost everyone can be classified as a junkie I say this because drug's like alcohol and benzodiazepines both work on the same neurotransmitter, GABA, at the same receptor, GABA A, and have the same mechanism of action, working both as positive allosteric modulators, both you, mum and dad drink. This is esseantially the same as taking a Benzodiazepine in many ways, just drinking alcohol is a more socially acceptable way of becoming intoxicated.
There's literally no difference, the state I was in was completely achievable from alcohol alone yet if that was the case you wouldn't be branding me as a "junky".

Statistically, the drugs that I have used in the past, I understand why this is hard for you to hear and listen to.
I bet you hear a lot about the deaths related to tobacco and alcohol are massive, but here is an accurate comparison to the drugs that I take from time to time.
Did you know around 400,000 people die a year from cigarettes, something as a collective me you and dad both use, without the thoughts of the damage, yes the situation that happened over the weekend must have been embarrassing and horrible for both of you, but it could be worse.
Think about this, what if you or dad or even me go to the doctor after you have symptoms of lung cancer or another deadly side effect of smoking? What do you think would happen then?
Around 100,000 people die every year from alcohol, yet another drug that you and dad and even me use from time to time, what if you or dad went to the doctor due to symptoms of a side effect of alcohol, how would that effect the family?

Now obviously I have no one apart from my self to blame for this situation but I believe that this is a turning point in my life, and I am almost glad it is being addressed.
I have to include this though, it is shown in most cases that parents smoking leads to children following the addictive behavior, basically passing on their own extremely destructive habit, very much similar to how a cocaine addicted mother will pass the dependency on cocaine to their baby.
It is only logical that children follow the behavior of their parents i.e - smoking and drinking in my situation.

Drugs follow a different path for me though, I notice the extreme harm of alcohol and the issues and dangers that can be caused by consuming it outside moderation, even with me it is a prime example.
Before I started drinking most weekends I was actually relatively loyal to doing to school, doing work, etc. After my outlook changed a lot, this experience has made me want to stray away from drinking. This is what I call the downhill turn.

From my experience all I have realized is that, you and dad for example find alcohol normal almost, purely because of social acceptability. If it was the other way around with weed being legal and alcohol being illegal I could purely guarantee that it would be the other way around.
In comparison we can look at how centuries ago slavery and racism against blacks was socially acceptable and widely so, now it is condemned, it is illegal, who's to say within the next 5 years that alcohol is made illegal and cannabis becomes legalized.
You may brand me a bad person, even change your entire outlook on me purely because you have finally seen that I occasionally do drugs, Saturday was a horrible experience and one that will never happen again. You may also brand be a bad person for taking a substance (such a benzodiazepines, weed and MDMA), but I cannot stress how irregular my use of these are.

The reason I say this is not to justify anything, it is to make you see this whole experience in my point of view, I see my friends, even you guys, even my self slowly committing suicide simply by taking a sip of a drink or taking a draw of a cigarette, why not do something that is scientifically proven to be less harmful for similar effects?

The two drugs I have tried and have used occasional are MDMA (Ecstasy, E's, Pellets) and Cannabis (Weed, Marijuana).

As you have both been brought up with the extreme propaganda that drugs are a bad thing, this letter will most likely not change your opinion on anything but to me it will clear the air.

The first thing I shall speak about is Cannabis, the harms, risks and even benefits.

Cannabis is a hard drug to explain as it gets branded and has always been branded as a hard drug, but can you explain to me why cannabis has been decriminalized and used as a legal treatment for patients with cancer and to air with the side effects of chemotherapy?
Cannabis is nothing new either, it is a natural growing plant, the difference between lets say a tomato plant and a Cannabis plant is little to none, both grow from seeds, produce flowers and produce fruits, the simple difference is one is branded as a drug and frowned upon by most of the world, let me show you why it should be acceptable and is extremely beneficial to the users of it.

Cannabis with the main psychoactive ingredient THC (effective where the "high" comes from") is legally perscribtable in Austria, Canada, Czech Repuglic, Finland, Isreael, Netherlands, Spain, Even in some cases in the UK (there are also drugs that contain another active ingredient called CBD, this is used in medicine to treat eppilepsy and to stop seizures) and in some states of the US, although it is still illegal under the federal agenda.
It can be used to treat things such as:
Muscle spasms, even if this is caused my something such as multiple sclerosis.
Nausea or sickness feelings, this could possibly be from chemotherapy.
It can be used as an effective treatment for those with anorexia or issues with eating, possibly from a chronic illness such as HIV or nerve pain.
It can be used to treat disorders that induce seizures such as epilepsy.
It also helps users with Crohn's disease.

These are strictly medical reasons that cannabis can be used, but it can also be used for other reasons, cannabis can be used to relax, reduce anxiety and reduce stress levels and all together take a 'load' off your mind and enter you into a small form of escapism.

A common misconception is that cannabis is an addictive substance, but this is incorrect, physically anyway, it can be subject to mental addiction but this will only effect people who tend to had addictive personalities.

Although being an illegal substance, cannabis is the most widely used illegal drug in the UK, it is pretty much the safest substance you can take, I will include a few sources and summarized information:

Cannabis essentially works in the same way as alcohol or many other drugs, the way in witch it effects your body is that the primary active compound delta-9-tetrahydrocannabinol compound in cannabis which agonizes CB1 receptors throughout the body, a receptor which plays a role in the bodies endocannabinoid system, which anandamide, a "feel good" chemical normally binds too, not dissimilar to how alcohol binds to GABA A receptors in place of the neurotransmitter GABA which causes the intoxication you know, or nicotine binding in the place of acetylcholine to nicotonic acetylcholine receptors.

Another issue with cannabis is that prohibition (similar to the prohibition of alcohol in america all those years ago), prohibitions have never been based off of logistical reasons or science, but in order to convince people that their legislation or working or required instead of logical approaches like drug decriminalization, taxation and regulation. They spread misinformation as policing these substances is a massive industry in it's self.

If we look at a country like America, specifically the state of California;
"California would gain the most from legalization. NerdWallet projects the Golden State would generate more than $519 million per year, which the website points out would almost fund the entire 2013 budget for California's Department of Parks and Recreation. New York would be second, with $248 million, NerdWallet said. Seven additional states would bring in $100 million or more from legalization, and 25 others would stand to make at least $20 million per year."
http://www.huffingtonpost.com/2014/09/22/legal-marijuana-taxes_n_5863860.html - Source

Yes cannabis might be a Class B drug, but when caught with cannabis there are little to no repercussions:
The first time you get caught the police give a cannabis warning for a first offence of possession – this is a written warning that does not show up on the PCN and should not show on CRB checks often carried out by employers.
The second time you get caught they give a Penalty Notice for Disorder – this is an on-the-spot fine of £80 for a second offence. You must pay this within 14 days or face going to court.
The third time you get caught they make an arrest if it is the third offence of having been caught with cannabis – this could lead to conviction in court and a criminal record. Although if carrying a personal sized amount you will most likely receive no charge and another cannabis warning will be give.

Most police officers are not interested in small time users, they want to stop main distributors as these tend to fund organised crimes meaning even if there was a chance of getting caught by police no record or name is tarnished.

Although this drug is still illegal there are multiple sources that support if becoming legal soon, most likely within the next 5 years.

https://petition.parliament.uk/petitions/104349
"Legalising cannabis could bring in £900m in taxes every year, save £400m on policing cannabis and create over 10,000 new jobs.

A substance that is safer than alcohol, and has many uses. It is believed to have been used by humans for over 4000 years, being made illegal in the UK in 1925."
This might give you a small insight that cannabis isn't some hard abusive drug, it is on par with alcohol and cigarettes, you both consume.

Another thing, police are starting to relax on small scale growers/smokers of cannabis as long as it isn't blatant, meaning it is steps towards legalisation.

http://www.telegraph.co.uk/news/uknews/law-and-order/11753350/Police-force-gives-cannabis-users-green-light-to-grow-drugs.html
http://www.dailymail.co.uk/news/article-3169435/Police-s-latest-potty-idea-no-longer-prosecute-smoke-grow-cannabis-small-scale-reduce-costs.html
http://www.mirror.co.uk/news/uk-news/cannabis-users-allowed-grow-drugs-6111926

Another thing to add is because you two are generally new to the idea of online dealing, there are a large amount of benefits in comparison to dealing with street dealers.
Buying online avoids the interaction with street dealers, gangs, etc. It removes you from the people that would actually come to your door, your words, not mine. It removes the chance of being robbed or even killed in situations, these are extreme examples.
You do not fund organised crime, people who sell online are similar to the people like us, the users who wish to stay away from the criminal world as such.
No risk of being sold dodge or cut drugs, this is because the vendors get left reviews and if they are bad, you simply wouldn't use them, it is almost like an eBay for drugs, this happens a lot of the time with street dealers, for example PMMA being marketed as Methylenedioxymethamphetamine.

I am not a stupid person when it comes to this either, to access the website I use a VPN (Virtual private network) like the one dad uses for his work, but a private one that logs no internet traffic.
Then I also use a program called TOR (Onion browser) this uses multiple layers of SOCSK5 Proxies that hide the IP of the VPN that I am connected to, so it is almost untraceable or non provable to say that I specifically ordered something.
UK to UK packages never go through customs of checks, so there is no risk of say a drug dog finding such, even if there were drug dogs, the package is well sealed and undetectable due to vacuum sealed products inside of an x-ray proof back.
Even if for some reason the package is stopped, police come to the door, I would have the right to plausible deniability, I can say I was sent the product at random and they cannot prove otherwise that this isn't true.

Another issue that I do not want you guys to think about is the fact that any money I goes towards drugs because this isn't true.
I actually have an online business and sell multiple things like e-books and programs, this only accounts for a small part of income but it is what allowed me to go out and do things when you and dad didn't give me much money.
The proof is here: https://gyazo.com/600b74495000acee017c11a8ced040e0

The point of me writing this is for you to not accept my previous use of drugs it is to educate you so that you know or can have safety that if it ever happens again I know what I am doing.
My experience last night was a complete mistake but luckily I do not take any form of drug if it can make you overdose, flubromazolam and Benzodiazepines require an extremely high dose for them to be deadly, although this experience has made me realize I should never NEVER touch this again.

The reason that you accepting my use of cannabis sometimes would really benefit me (even if on extreme occasion and not in the house) would benefit me as it relieves a lot of stress and although I might not seem to be as affected by issues as you are.
Like for example Uncle William and his stroke, I am devastated that he will probably never be the same, Gran, I heard you speaking about that care home it almost brings me to tears thinking about it because I have no form of helping her.
Mum, being away almost every weekend, always being stressed, I genuinely believe you are depressed sometimes and I feel like I can't do anything. Dad, fair enough you are allowed a drink but it is the fact that everything seems to stack on top it is just a big block sitting on top of our family and I need a form of escapism.
If you seriously consider it, I had an issue, I was pretty much an alcoholic for a solid 2 years, apart from recently, I bet you can't think of a weekend that I wasn't drinking.