Heavy bleeding two days in a row 3 days after period ended?

I have endometriosis, so naturally I have a very heavy and painful flow that lasts around 7-8 days. I'm used to crazy periods, but this month I had a 7 day long period which ended this past Friday, just to return with a vengeance three days later? Has this happened to anyone else? I'm losing a pretty gnarly amount of blood and Midol can't touch these cramps. I don't know if I should be worried or if this could possibly be a side effect from stopping birth control a few months back?