Bi-Polar?

I always have these violent mood swings. One second I am so hyper and happy, the next I am sad and depressed. One of my friends says I have Bi-Polar disorder, or violent mood swings that the person cannot control. I don't think I can control them, which intensifies my beleif that I have this dreaded disorder.
I have no guts to tell my parents, or even ask them if they think I have it. I don't want therapy, ot medications, I will just deal with what I have.
My depression problems are the worst though. It starts out with my being quiet, not thinking or saying anything, but then it goes to thoughts of suicide. I think about how better the world would be without me, and how no body would care. Once I almost did commit suicide, but I had nothing to do it with, I was outside, on a bench. Knowing I had almost killed myself worries me. Someday I will crack and just do it. Blank out like Forth of July fireworks.
Anger is second to worst. I get angry for no reason and take out my anger on other people. That hurts them, which hurts me. Anger fades away after a couple of minutes, unlike depression.
But either way, I beleive I have Bi-Polar disorder