I don't wanna be depressed but somehow can't help myself with it?

In my life there are hell lot of reasons for me being depressed and i won't count them now. My overview is that im 19yr old geeky, nerd boy, with hell lot of absurd thoughts. I socialize seldom as i hate most people and their thought process means its kinda difficult to find one like me. In having my main final exams and im less concerned though i may easily score average. But lot of things occupies my mind...and lately im also depressed because of not confessing a girl i like and she don't give a damn f*** about it. can anybody has any suggestions.....its like my life is going through a melancholy and lately ive recovered from severe depression and having those thoughts again it haunts me.... people close to me suspects my behavior they ask if its all right but i guess none can understand me, and i don't like to open up with peoples.