I have a fear of social situations. How do I act more outgoing?

I want to be outgoing so badly you don't even understand. I am not exactly shy when I'm talking to someone one-on-one, I'll have a good conversation with them and usually talk a lot. But when it comes to being in a small group of people around 5-10, or a classroom, and anything larger, I literally have a fear of these kind of social situations. I can't talk to more than three or four people at a time, otherwise I get so freaked out and act shy and quiet. I'm paranoid that nobody will like me. I also feel like I don't fit in with anybody and everyone is so outgoing in these groups of people and so fun and exciting and they like to party and they do fun stuff. I have never been to a party before (like the "big" ones), I've never had a sip of alcohol before, I've never had a boyfriend and I've never done anything illegal or interesting that these people have done that people seem to like to talk about. Its not like I want to be a drunk sex-obsessed crime breaking partier or anything, but I want to feel like I can understand what everyone else thinks is interesting and I just want to fit in and for once have something interesting to add to a group conversation instead of sitting and listening to everybody's fun life while I sit at home and twiddle my thumbs, wishing I could make friends so easily (I have a terribly hard time making friends) and feel like I actually belong in this college setting. So I digress, but seriously, what can I do to be more outgoing and actually talk to people? I'm sick of my phobia of people and I hate myself because I'm this way. It sucks and you have no idea how terrible it feels. Please don't say its impossible to change. I hate the way I am. Any help would be greatly appreciated.