Miscarrying ?

I have been on the birth control Trivora for over a year now. My periods are typically very light now, and flow from (starting sugar pills on Sunday) Monday to Thursday. 3 weeks ago, while my period was ended (Friday), I had intercourse without any protection. I was still on sugar pills at the time and did not start taking them again until the following Sunday. Nine days into that Birth control cycle, I missed one pill. That night I began spotting, which I expected. However, the spotting turned into a period with a very heavy flow, with bits and chunks of tissue. It has been 5 days since the skipped pill, and I have been taking my pills consistently since, but I am still bleeding heavily. Because I had completely unprotected sex, I knew I had the possibility of being pregnant. With this bleeding though, I am worried that there is something wrong, like I may be miscarrying. Can you please help me understand what is happening?