This is fantastic. I left school at 16 and went to university at 19 and going to university was an amazing experience for me, and I was sober!
So there are a few things that worked for me. First of all, I told people I didn't drink alcohol, which meant that when I went to the student bar, there was always a coke waiting for me. Secondly, I joined a lot of groups. I went to gigs, language groups etc and ended up creating my own group. I created flyers for a sober hangout and after a few weeks, sober students started turning up and we went to gigs, talks, amazing concerts or just sat around in the bar drinking soft drinks!
This is an amazing opportunity for you and the best advice I have for you with regards to university is: Do not be ashamed.
My first year was spent ashamed that I was dating a woman, and it was a waste of time. University is an amazing experience and there is no reason to care what close minded people think of you. Do your own thing and I guarantee you will carve out your own amazing life.