Moral Dilemma: The Drink

You're experimenting. The fact that you're now troubled by your experimentation should be a pretty good indicator to you that drinking and drugs isn't in your make up, for what ever reason.
To me, there is no "Moral Dilemma" here. It's obviously not the thing for you. Why make the solution any more difficult than the "facts" that have already presented themselves to you?
How you handle things might be more of an issue that should you handle them. It might be necessary for you to find a different group of people to associate with, IF your present group of friends can deal with your choices not to take part in drinking, smoking, and what ever else they are involved with.
If nothing else you can always claim to be the permanent "designated driver".
But keep in mind that if they ever get busted for drugs, and you're with them, you're going along for the ride, too.