University is a huge, vibrant metropolis filled with people that would gladly be your friend. What the hell is the point of wasting it when clearly you could be going out and having fun?
Smile. Have some good Body Language. You need to loosen up and smile more. I read somewhere that you're something like 70% more attractive and approachable if you smile. Don't look as though you're insecure, keep eye contact and keep your thumbs out even if you've got your hands in your pockets. Don't cover your abdomen when you talk to people, and don't touch your face when you talk. Don't play with your hair, and keep yourself together. Awkward silences are only awkward when you point out that they're awkward.
Be more sociable. Join a society, sit next to people in lectures for ***** sake. Nobody's going to think you're weird or that you're going to rape them if you sit next to them and say hi before the lecture starts, or ask them a question in the middle, or comment about something. Join a society and introduce yourself, don't just sit there like a **** thinking everyone's going to ask you for your name - it's more than likely they're the same as you are.
Sit next to people. This pisses me off the most in lectures. Granted, you may want to sit alone and learn, but those that do are obviously isolating themselves from human contact. Then, they complain about having no friends. Honestly, sit next to someone and ask them their name. Introduce yourself. People aren't going to come flocking around you, it's just not going to happen. Even if you're the most insecure person in the world, you can still manage to make a few mates off your course.
Also, seminars/workshops. HONESTLY, introduce yourself and tell us who the hell you are. If you're in a small group of people who talk over you, think of something to say, or like, try and find another group. You've got to present yourself.
I'm not by far the most confident person out there, or the most attractive; but faking confidence is something I can do, and I'm sure that it's landed me a few firm friends. Fine, there are those really social and outgoing people that still intimidate me, and I still can't ask them to do stuff with me yet, but hell, it's going to happen at some point if you just keep your chin up and stop bitching about it 24/7.
Also, forget your flatmates if you don't get on with them. A lot of people I know don't get along with their flatmates either. Meet people on your course or in societies.