I've just finished my last year at uni and I was in the same boat, and it was utter rubbish. I used to have people I would talk to occasionally on my course (a handful) and then my flatmates (who were all on a separate course to me), but that was it. I lived with different people every year in halls so that I had more chance of finding friends and sticking with them, but although my flatmates are lovely and I get on with them really well, I cant really say I've had anyone that I've 'stuck' with the entire time.
It sucks and there has been many times where I've sat and thought "is it me that's the problem" even though I do like going on nights out like other people did. However for some reason none of the people I knew seemed that bothered about being close friends with me and I only found that they bothered with me when I used to contact them, I never found that they would contact me out of the blue every now and again, I was always doing the running and doing that for 3 years gets a bit boring.
It's a very lonely time if you don't make the effort but for the whole 3 years I have done nothing but make the effort and I cant understand it because I am a normal person who likes doing things, going out, having a laugh and just general things. But for some reason, it just didn't work out.
If I could advise you on something, try to move in with different people you don't know every year, so that there's a new chance of meeting friends.
My first year flatmates were so nice and I was too much of a bookworm to ever go out with them and I definitely missed my opportunity to have an amazing friendship if I had made the effort with them. My second year flatmates were not nice because they all lived with each other the year before and they definitely didn't want anyone coming into their 'friendship circle'. My third year flatmates are lovely but by this time, we are all on different courses and they are on placement so never at home (and they have their own friends in and out of uni), so this year our friendships have been more casual with each other. I don't regret meeting my third year flatmates because they are lovely but I wish I had made more of an effort with my first year flat and maybe things would be different.
To be honest, if I wasn't the type of person to get on with my studies, I would have had a breakdown by now because if I wasn't doing work I would just be alone. I'm just thankful that I can move out now because the whole 'uni social experience' has been very disappointing.