It sounds like you really needed to get that off your chest. When i'm feeling down i do something i enjoy, listen to music (not depressing stuff), play a game, have a bath... just generally chill out. Go sign up for some societies and get to know more people. I'm an overly confident person, i can talk to pretty much anyone without fear of being rejected. I'm happy with how i am, and if people don't like it, then it's their loss. Why don't you go to a bar one night, and start chatting with random people? If they don't chat back, move on.
You sound really down in the dumps, see if you can find the root cause of your problems, and work on them. If you want a more friendly chat and have MSN feel free to PM me. I've been through a rough patch myself this past month, mainly because i split up with my girlfriend of 27 months, so i can hazard a guess at how your feeling.