I don't know why I still keep this thing

I find myself at the trough of depression again. This happens a lot, but it still sucks when it does. It's all sorts of stuff that brings me down: grades, girls, mainly girls. I have no idea why, but for some reason I just can't be happy alone. I've been trying like crazy to find someone, and everyone says it'll happen when I stop looking. I can't stop looking! I'm constantly subconsciously analyzing almost every girl I meet. It really bothers me seeing other people in a relationship together, because don't have that. There's almost no one close to me that I can connect with. Also, whenever I try and get close to a girl, she declares us good friends. I'm getting really tired of having exclusively male friends. I love my friends, but I don't have any friends that are girls.