I also have trouble not drinking at my age. In high school/college you are surrounded by people who can drink for fun and it's so socially acceptable that I didn't even realize I had a problem. Sometimes my drinking was praised because I could drink more than friends.
It's very hard to find people my age who do not drink/do drugs. People who don't have a problem with it just do not understand, and I'm not sure they ever will.
Are you worried about being around your friends that drink? When you go out with your friends is it always at a bar or surrounded around drinking?
Going to AA/counseling is great. I haven't been to AA (yet), but I've heard you just need to keep going...and going. Do you have a sponsor?