I am very similar to you and go through periods of not drinking. This time, I have made a commitment to be sober.
I always used to go out with people for a 'drink'. After they left, I would go find another group of people to have a 'drink' with. I was a party animal but hated it..
When I dont drink - I just tell people - dont feel like it and change the subject OR my doctor told me not to drink OR that I am on some pain killers ( I play a few sports and am on pain killers when I hurt myself) OR that I have a game at 6 AM tomorrow morning and dont want to mess it up.
In reality, it is more in our head than anywhere else. People are consumed with their life/issues/problems and dont really care a whole lot if you drink or not. The people are there to satisfy their needs/cravings which in reality have no true bearing on what you (or I) are doing