I'm 23 and I am an alcoholic, and I have found that I fit in quite nicely in the rooms of AA. It was my last resort since I didn't think someone 23 could be an alcoholic but I needed to make sure I tried everything to stay stopped. AA was the only thing I didn't try and it's worked better than anything else by far. There are plenty of people I know who are younger than 20 and in AA. I actually know quite a few people who never even had a legal drink since they got sober before 21.
You are not too young, if you think you need help go for it. It sure beats waking up not knowing what you did and how you got home. Not to mention the lifestyle that comes with sobriety. No lying, no cheating or stealing. It's quite freeing.