+1 to what FitPolak just said.
I have the same experience as you that during my teens I started to have these "cycles" of feeling good and bad. I don't think it counts as manic depression or being bipolar as for me because the feelings are not really extreme. Yes, I have thought about suicide, but was never close to actually do it. My "manic" phase is just feeling euphoric, not some crazy over the top stuff that I know some people could do when they're manic.
I don't think you can ever cure yourself completely, but you can control your life in a way so your condition is not worse. There is medication for depression, but as it eases your negative felings, it also dulls your positive feelings and this is something I would not like for myself.
The worst thing I did was turn to drugs and alcohol. After maybe 5-7 years of heavy partying, trying to fuck every chick and live the "hedonistic lifestyle" I got sick of it and stopped. Now I'm at the gym 3 times a week and run/swim 3-4 times a week and I have to say I feel great. There is nothing better for your mental health than taking good care of your body. Eat good nutritious and fresh food etc.