You are experiencing one of the most common problems with settling into university life - fitting in.
The reason why all the people around you are drinking so much is to mask their inhibitions and make themselves feel like they fit in - because inside they feel exactly like you!
Stick to your guns, and wait for the intial heady nonsense of being away from home with no-one telling them what to do to wear off, and it will, quite quickly.
In the mean time, do socialise, and ignore the entreaties to drink if you don;t want to. Secretly people will actually envy your stance, but be too shy to admit it. You will find like-minded people and build up a circle of genuine friends who enjoy compnay and conversation instead of personality by-passes and early morning vomiting fits.
Hang in there, and be strong - which is what you are, and let the waker ones go their own silly way.
You will be glad you stuck it out, promise.