My father was an alcoholic (and not much of a father as a result), so I always said I'd never go down that path. Well, you can guess what's happened -- I've become an alcoholic. How did this happen? — J.McN.
Surely one of life's greatest puzzles is why we keep on making bad choices in life, even when we know they'll only hurt us. Even the Apostle Paul experienced it: "I do not understand what I do. For what I want to do I do not do, but what I hate I do" (Romans 7:15).
I don't know why this has happened to you; I can only guess. I do know, however, that people often turn to alcohol to escape from their problems, and perhaps this is the case with you. After all, you didn't learn from your father how to deal with problems; his answer was to escape from them by turning to alcohol. Now this has become your "solution" (although in reality it only makes your problems worse).
The real question, however, is this: What should you do now? You've already taken the first step by admitting you have a problem with alcohol. Now take the second step by seeking help to deal with your problem. Your doctor or pastor or other professional can point you to programs in your community that have helped others, and may help you. Don't be ashamed to admit your problem to someone who can help; it will only get worse if you don't.
Most of all, seek God's help. God loves you, and unlike your earthly father, your heavenly Father will always be there to help you. Begin by asking Jesus Christ to come into your life, and then ask Him to help you become the person He wants you to be.