I was 19 when I started drinking and was a full blown alcoholic by my early twenties. I only wish I'd been as honest with myself as you're being now. The fact that you've readily acknowledged a bad problem is good.
I attend 3 AA meetings a week, and each one has a number of very happy, healthy 20 somethings that have decided to knuckle down and change their lives by eliminating alcohol. I can't help but think what enormous favors they are doing for themselves by tackling this problem early.
You can do it