What Does Backache And Fainted Red Vaginal Discharge Indicate?

I usually get my period at the end of the month ,my last period was dec 24th and I didn t get a period for January .. My periods are usually regular and I ve also never missed a period . This morning I started bleeding but the blood looked old (brownish ) I thought maybe it was implantation bleeding since it looked old and I missed a period .. As of right now the bleeding has gotten a bit heavier not as heavy as my normal period and when I wipe it s not bright red like usual it s more of a fainted red/pink .. I also have a backache not cramp like and the backache started a couple days ago . I m very confused.. Could it be my period or is it actually implantation bleeding ?