If i show signs of bipolar or any other mental disorder?

I have had a really tough past full of problems, like cancer when i was six, my father left in the middle of my treatment, and was bullied in school and ended up dropping out, plus the girls i have dated were really hard on me, and i have always had feelings of sadness and emptiness, and my old doctor said i have depression, but i have really bad sad moments and really happy moments, i get really happy for a period of time and then i crash and then i just wish i would die, im 20 now and the past month it seems like its been nothing but sad, the emptiness and the hopelessness has just seemed to take over my life i get a few hours here and there that i get happy, but then i crash harder each time, i have not been able to eat right in three days i'm going through a break up and it probably is playing the most major role in the sadness lately but, i am just looking for some advice or pretty much anything, well anything but dumb remarks or hurtful things so, please just drop me some answers and go easy on me lol :D