How much damage alcohol can cause to the body depends on a lot of factors, but don't let the fact that you got a "clean bill of health" fool you. You're still young, so there's that- but if you keep up with what you've been doing there will be health consequences. None of them are good: pancreatitis, cirrhosis, heart problems, high blood pressure and increased heart attack/stroke risk, increased cancer risk... It can and will catch up with you. The fact that you're still young is probably the reason that the damage has been apparently minimal. I wouldn't for a second think you're "immune" to alcohol's ill effects, or fishing in the same pond as Keith Richards. Put a stop to it while you can.