while ($stmt->fetch()) {
    if ($teacherusername == $dbTeacherUsername && $teacherpassword == $dbTeacherPassword) {
        if ($dbActive == 1) {
            $loggedIn = true;
        } else if ($dbActive == 0) {
            $loggedIn = false;
            echo "You Must Activate Your Account from Email to Login";
        }
    }
}

if ($loggedIn == false && $_POST) {
    echo "The Username or Password that you Entered is not Valid. Try Entering it Again";
}

while($stmt->fetch()) {
    if ($teacherusername == $dbTeacherUsername && $teacherpassword == $dbTeacherPassword) {
        if ($dbActive == 1){
            $loggedIn = true;
        } else if ($dbActive == 0) {


            $loggedIn = false;

/****************************
 *
 * at this point, $loggedIn == false.
 *
 ****************************/


            echo "You Must Activate Your Account from Email to Login";
        }
    }
}

/****************************
 *
 * at this point, $loggedIn == false.
 *
 * since $loggedIn == false and $_POST is truthy, your if statement will get entered.
 *
 ****************************/

if ($loggedIn == false && $_POST) {
    echo "The Username or Password that you Entered is not Valid. Try Entering it Again";
}

$active = true;

.
.
.

if ($dbActive == 0) {
    $loggedIn = false;
    $active = false;
    echo "You Must Activate Your Account from Email to Login";
}

.
.
.

if (!$loggedIn && $active && isset($_POST['formInputName']) {
    echo "The Username or Password that you Entered is not Valid. Try Entering it Again";
}

while($stmt->fetch()) {

if ($stmt->fetch()) {
    if ($row->$dbActive) {
        # valid login
    } else {
        # needs activation
    }
} else {
    # invalid login
}

if ($dbActive == 1){
    $loggedIn = true;
} else if ($dbActive == 0) {
    $loggedIn = false;
    echo "You Must Activate Your Account from Email to Login";
}

if ($dbActive == 1){
    $loggedIn = true;
} else{
    $loggedIn = false;
    echo "You Must Activate Your Account from Email to Login";
}

if ($loggedIn == false && isset($_POST['somefield']) {
    echo "The Username or Passwor...";
}

if ($loggedIn == false && !empty($_POST) && $dbActive != 0) {
    echo "The Username or Password that you Entered is not Valid. Try Entering it Again";
}