Am i bipolar? Am i insane?

I'm 17 and I always get angry and upset for no reason. my mood changes so easily. Everytime i get angry i throw things, and i often imitate strangling and killing someone by punching the walls and strangling the pillows. I've been experiencing chronic mood swings since i was 14. I get hyper, then i'd get really tired to the point where i lose interest in the things i enjoy doing. Then i'd be really happy at one point, then after a few minutes i'll get so angry that i'll start crying for no reason. I also constantly think of ways to kill myself. I even tried slashing my wrists once and overdosing on pills and i also hit myself. I have no idea what's going on with me. It's getting worst! I'm also hurting the people around me...when someone asks me a question i would just yell at them. I also tend to talk to myself out loud, sometimes i ask questions in my mind then i would talk out loud and answer myself. I even laugh or yell at myself without knowing that i'm doing it. Am i insane? People around are starting to get scared. I have no idea what's wrong with me. I just pretend that im alright in front of my peers so that they wont find the need to ask questions. I've also noticed that im beggining to get anti-social. Sometimes i run to my bedroom when there are visitors, i'd also reject phone calls. I also sleep in a lot even if im not tired. I recently missed 52 days of school because of this. I used to be so interested but now im just always angry and upset. I hate myself all the time. I have no idea what's going on with me. I'm getting really tired of this because it happens so often almost every week. I can't take it anymore, im hurting my family and frankly they'd be better off without me. My moods are changing a lot and im crying a lot for no apparent reason that it results in constant migraines. I wanted to go to a doctor but we have financial problems. Somebody tell me what's wrong with me PLEASE. I wasn't like this before. I need help!