Man up dude.
I won't beat around the bush here. I'm drunk most of the time I'm not at work. Hell, I'm drunk now. Had a 6 pack during the Neverending Story and then a good 1L of cask wine so far. This is on a Sunday; I *start* work tomorrow. This is as fresh as I get.
If you have a problem with your friends drinking whilst you don't, then that's your decision. If your friends have a problem with you not drinking whilst they do, then that's they're decision.
You weren't clear why you didn't drink in the opening - in my experience, the majority of people who say 'oh no, I don't drink' when offered a drink are that way because of choice, rather than necessity. It's like a vegetarian saying 'oh noes I don't eat meat what if I go to a BBQ?'. Guess what? No one's problem but your own.
Maybe you need new friends? Remember, you can choose them. And if your friendship is based upon whether you drink or not smacks of primary school 'stranger danger' bullshit to me. Act your freakin' age.