So shocked to have seen someone post this, I had this exact same problem happen to me a few years back!!! I used to be heavily involved with drugs and still use them them on occassion (however I'm starting to get myself away from it all). Anyhow I got tangled up with a group of heavy users and we'd do pretty much anything we could get our hands on, eventually ended up making me very mentally ill and depressed that I finally cut my losses and dropped out. Recovered mostly now and am going back to uni this year, my advice would be to get yourself out of the situation and disassociate with anyone who does them. Reason being you will quickly be (as you found out) excluded from social groups and most people will look down on you and you'll be put in a box and isolated. Cruel I know but it's just the nature of society in this day and age, get yourself out of it while you can and for the love of god don't let it mess up you're education and set you back like it did mine.