Do I have bipolar disorder/depression?

I think I have bipolar disorder or some kind of depression, there is definatly something wrong but im not sure which one. Not 1 day goes by where I dont think about killing myself, I feel I deserve to die, I use to cut myself back in school. I have terrible moodswing, I dont mean from bad to good I mean from amazing to awful I suddenly feel amazing, smiley and so good then in a matter of seconds I can go to crying, thoughts of suicide. I have rubbish sleep, have put on a stone and a half in the last year. I always wonder why the hell I was even born. I feel stressed and impatient all the time, sometimes I find it hard to make decisions, even when im chosing a chocolate bar, the other night, I woke up from my sleep in some kind of fit, I couldnt breath, I was gasping for my breath and my heart was beating so fast, I dont understand why, because I was sleeping, I feel like I’ve lost my identidy, I dont know who I am anymore.. And have lost most of my confidence. Sometimes I find it hard to keep a convosation going with people. I dont know why.

Someone please help me, I cant tell my parents, they all ready think im wierd. And im scared to go to the docter, incase they make me take antidepressents or send me to some kind of mental home, I feel like im in a trap and theres no way out.