How do I fix this feeling?

I am just so frustarated with people lately. First off people in one of my classes. One kid snorts almost everything and alls he talks about is sex and he is just so stupid. Then all of my friends just are drifting away and they sorta ignore me now but not on purpose. A girl I liked for two years we were pretty close and had a thing going on and now that it's over she won't talk to me she won't even look at me unless she thinks I don't see her looking at me. I didn't do anything to her. She kissed me and was all over me and she knows I like her and then she just stops one day. I started liking someone else while she was ignoring me and she was all over me but now she like hates me or something. What do I do to get everyone and her to talk to me again or more often?