I cant stop drinking. How can I stop?
You are alcohol dependent, and will need help.  You can't just do it on your own.  Try any AA meetings?
What do they teach you at AA meetings?
They have people who are alcoholics who have stopped drinking.  Their purpose is to "stay sober and help other alcoholics achieve sobriety." Go to a meeting!
What happens if I relapse?
Well, I think most of them have had the recurrence of alcohol use after they quit.  They could help you handle it and start again.