Absolutely go to uni. I'm a pretty introverted person, with anxiety and depression. I've never been a big drinker - I've never even been drunk as I was teetotal for my first year and a half of uni, and have now had to stop drinking because of medication. You'll still be able to make friends no problem, there are plenty of people who are a bit more introverted and don't drink. You can join societies and find people you'll get along with. At my uni anyway, the big sports clubs (hockey, rugby, lacrosse etc) have quite a big drinking culture, but a lot of the smaller clubs or the non-sport societies are much more chilled.