Why am I no longer a happy person?

I used to always be a happy person but lately that's changed. I'm no longer a happy person like I used to be. Looking back on it I don't even understand why I used to be happy. My life sucked then and it sucks now. Little has changed but somehow I used to manage to be a happy person. I don't have many friends partly because I'm not very outgoing and partly because I always manage to find the faults in people and can't stop focusing on the negative. There are very few people that I even want to be friends with. In high school I rarely went out on the weekends but it didn't bother me that much. Now I'm a college freshman and I don't go out on the weekends and I hate it. But I don't even know what I'd want to do if I were to go out. It seems like all there is is frat and sorority parties and I can't stand frat boys and sorority girls which my school is full of.