Birth Control

So I have been in birth control for five months now, because I was becoming anemic from having my period to often. Last month I got my period in the middle of the twenty eight days. But I had missed a pill so assumed that was why. But now I am getting my period while on the pill again!! I shouldn't get it for another five days. But my back already hurt, my gut is super off and I already have my period. Does anyone else have this problem or have any suggestions on what to do? Is there something wrong??