Miscarriage? Pregnancy?

lately things like this has been coming out of me. It's been brown for about two weeks til Wednesday when it turned bright red and a big "blood clot" (that's what it looked like) came out. I am currently on birth control and tomorrow I start my last week which is my period week. But before I started taking the pill I had sex which I bled alot during it. And that was the first time I had a "blood clot"