A few weeks ago I noticed vaginal bleeding after a bowel movement at first it was red but it soon turned black and persisted for three days. I thought maybe it was implantation bleeding. But I passed a bowel movement yesterday (four days after my period was due) and noticed more vaginal bleeding. It didn't go black and so far it's not as heavy as my normal period but I am having abdominal pain. I'm 18 years old and I'm not on the pill and other than a few stomach issues in the past few months and low iron levels I am usually healthy