Nearing the end of high school, feeling depressed.

I'm in my senior year of high school, and while on one hand I think I have a lot to be proud of such as good grades and SAT scores and such, I feel like I've missed out on a lot of the high school experience. I have a healthy amount of friends and a few really close ones, but I've never had a girlfriend or been to a party, and these are things that I actually want to do. I think a lot of it comes from the fact that I'm really cynical, misanthropic, and especially judgemental, and this really makes me hate who I am. It really makes it hard to talk to people who aren't already my good friends, and I just always feel awkward when talking to people. Is there anyway I could change this around so I can enjoy these last few months?

Edit: I also generally put up a really positive and smiling exterior, but I let my shitty mood slip out a lot.