Mood swings. What should i do?

I am having mood swings, irritability, anger, and sense of revenge. Sometimes I feel too haapy and there's a sense of joy. Bt at the same time even the smallest of the things can make me angry. I loose my calm, and will shout on everybody. This lasts for about some roughly from 30 mins to few hours. I feel like crying. And then again a feeling of empty Ness grabs me. I feel sadness. A sense of guilt. Severe pain. I don't socialise much. I only talk to a few people and someday I don't like to talk to them even. I want to lock myself up in dark room and don't want to come out of it. Don't feel like doing anything or eating. I just want to sleep. Sometimes I take sleeping pills so that I can sleep easily. Sometimes I feel that wat I am doing or saying is wrong, in spite of knowing all the consequences that I might have to face, I can't resist myself from doing it or saying it. then I feel sorry again. this is happening for almost 2 yrs now. what should I do?