<?php
    if ( is_single()) {
        $categories = get_the_category();
        if ($categories) {
        foreach ($categories as $category) {
            $cat = $category->cat_ID;
            $args=array(
            'cat' => $cat,
            'order' => 'DESC',
            'post__not_in' => array($post->ID),
            'posts_per_page'=>2,
            'caller_get_posts'=>1
        );
            $my_query = null;
            $my_query = new WP_Query($args);
                if( $my_query->have_posts() ) {

        while ($my_query->have_posts()) : $my_query->the_post();
    ?>