I have been noticing sudden changes in my personality, what is the explanation?

For the past couple years, I have gone through quite a bit of "hell" you could say. My father and mother had a very messy divorce such as abuse (verbal and physical), illness in the family (Father gets parkinsons), I have 2 suicide attempts (both I wind up in a psych ward), and this all happened from the period of my life when I was 12-15. Through this time I have noticed a sudden, and extremely rapid change in personalities every once in awhile. I become very confident, happy, yet impulsive person one moment, and a depressed, extremely anxious, "crazy" teen the next. I am still 15, almost 16 and I feel like I have more than one person inside of me, they're fighting for me. It caused me to almost kill myself again tonight, so I want to get this fixed. I cheated on my girlfriend and I don't remember a thing. I blank out for moments at a time. Are these symptoms of multipersonality syndrome, depression, teenage years, or anything else? What should I do?