13 day bleed?!

Natalie
So I've been on birth control for about 2 months now and I'm supposed to get my period every third month. I got it two weeks before the placebo pills. I gave my Gyno a ring and she prescribed me stronger BC pills. My bleeding was super heavy for all 12 days I bled. I started the strong medication and they reccomend a flush. Take 3 pills one day, 2 the next and then continue regularly. When I finished the flush I had no bleeding but when I went back on it regularly it came back and heavy as ever. Now for 4 months before this I've been having pelvic pain. I had an ultrasound and exam which showed nothing. Been tested for PID and it came back negative. Does anyone have ideas? It isn't digestive or urinary I've been tested for those too.