I think I have split personalities?

Ok so somedays I am super social. Giggly, happy, funny, sarcastic. The for some reason the next day I will do a 180. I will start to right dark poems. Write all over myself, be very very quiet. Blast hard rock music, relieve bad memories to make myself feel bad, and cry. So this can happy for a week on and off. Be gone for a month, then back again, then the next day im all good again. I have been through some things. Im not sure if this is the cause or not so ill just be brief. My parents split when I was 5. I went with my mom. She was a horrible alcoholic. I had to take care of my self basically she was never home. Would threaten to kill herself, even attempted it once with a knife to her wrist in front of me when I was 12(lucky though she missed the major vein). My dad was barely ever around. When he was he was an ok dad. I would have to stay at friends houses because if not my mother would shout obscenities at me or throw objects at me. Finally I could take no more so I ran-away to find my father at 13.( I didn't know where he was at the time) I went all the way from west palm beach to orlando. Once I found him, he took me in. That year 2 of my closest family members died, drug overdose. I feel guilty for leaving my mother, bad as she was I was the only thing keeping her semi ok.... alive even. Like I said though Im this Straight a student one day who does very well socially, very obedient. Then like clockwork a few days later all of a sudden theres this dark law breaking girl who would do anything for the thrill and could not give a **** what the consequences would bring.