I Am A Female, And I Just Recently Came Off

I am a female, and I just recently came off birth control (depo provera) I have been on and off for 3 years. But have gotten 6 months worth straight this year. (If that makes sense) I will bleed one day pretty heavy, to the next day nothing at all, then to brown discharge, the days I'm not bleeding my back is hurting extremely bad I can't sleep, I'm a cry baby, my stomach hasn't been feeling very well. I don't think I'm pregnant. But I just don't feel very well, and wasn't sure if it was because I had been on the birth control for so long and now that I don't get it, if my body is just trying to deal with the change?