You seem to enjoy it for the most part,and the things you dont really like can all be changed.
We all know people who dont socialise with people in their own hall/flat , but do socialise with others, there is nothing wrong with that and you shouldnt feel alone in doing so.. many people do it. You get invited out, you go out, etc .. the more you go out the more you will get invited.
It is not too late to join socieities and make friends, just have a quick chat or email to a few you are interested and see what can be done.
On one hand i would say that you should stay, its only been 13 weeks out of a whole year .. it will get better if you think about the points above and others.
but on the other hand, i wouldnt really advise someone to stay at uni if they dont like their course, which seems to be your main concern.
Not liking your course can lead to less motivation, less interest in the subject so less work done.. work standards fall and you fail a degree or come out with a 2.2 or worse. This can happen.. or you do fine but end up feeling like you do now for 3 years.
So, if you REALLY dont like your course that much, and see no way of it improving, then maybe you should get out now.. but if its not thaaat bad then i'd advise waiting a little longer.