Consider yourself lucky that you admit you have a problem, that seems to be a big hurtle for many. My biggest piece of advice is to stay away from those you do it with, your one friend in particular. No matter how long you have known him, the realtionship you both have is based on coke, and he doesnt seem to care that you want to quit. So really, he isn't a friend at all. Spend time with the one friend that pushes you to be straight, and ask if you can lean on her for a while, as a support network is your best bet. I've had friends that quit their well-paying jobs to move to get away from coke influences.