Why is my period brown ?

I am 16, and i began taking birth control around march. I took the depo shot once and after that i stopped taking it. Siince the beginning of April my period has not stop. It would stop for about a day then begin again, so therfor ive basically had my period for about 2 in a half months now. And when i would bleed it would be a very dark brown color, why is this happening ? is there anyway to stop it or help it ?