Why do I get a feeling of gloom or a sadness when I hang around certain people?

A long time ago my cousin and my best friend betrayed me. I never had a lot of friends I had kind of a tough up bringing my parents broke up when i was 5 and then we had to move in with my moms bf when i was 10 he was so emotionally abusive. Then when i was 15 i feel in love (at first sight) with a guy then i find out he has the same last name as my stepdad WTH! not related though. My parents sent me away to a group home after only 3 months off the best time of my life. Everything went down hill from there i almost killed myself not kidding I need some input what should i do I Am such a loser