bleeding heavily Did I have a miscarriage?

I have been on the birth control pill Microgestin for a few months and have been having unprotected sex several times a week the whole time. My periods were always normal up until this month; when I stopped the hormonal pills and began the iron pills, I had no bleeding, only thick clumps of mucus ranging from pink to brown (but never blood red). On the fifth day after I was supposed to start my period, I had sex and I bled slightly during. About 10 hours later, I began bleeding heavily and a rubbery blood clot about the size of the tip of my thumb came out. Since then, I have been soaking through thick pads every hour with more large blood clots, some of which are rubbery/stringy in consistency. I have no cramps or bloating, just very heavy bleeding and clots. Is it possible that I could have been pregnant and then miscarried? If not, why did my period take so long to come and why am I bleeding extremely heavily with multiple large clots?