Some advice please

Okay, so I have PCOS and my doctor had put me on BC to keep my periods regular. When I started taking them I would get these horrible migraines, with me being in school and working, I couldn't do it so I stopped taking them. I had recently tried them again, but a lower dosage and halfway through the pack I started my period and I have been bleeding for 12 days. Before this I haven't had a period since August, I'm not bleeding uncontrollably, it gets heavy at times to where I have to change my tampon every 4 hours, but then it will stop for a couple hours to a full night then start up again. I have little blood clots, about this size of a pea, maybe a little smaller. I stopped taking the pill yesterday. I am sexually active and we didn't use protection, I took a pregnancy test a couple days before starting the pack and it was negative. Now I'm just worried if it was too early and I was and this is a miscarriage or if there's something wrong like tumors or cancer to where I won't be able to have kids. If I don't stop bleeding in the next couple days I'm going to the doctor, but I just wanted some advice on what it could possibly be, or if anyone else had this expirence?