Have I had an early miscarriage or just a bad period?

I went to the clinic for the morning after pill because I had had unprotected sex with my boyfriend about a month ago. She gave me the emergency pill and I also got put on the contraceptive pill and she told me to come back in 3 weeks for a pregnancy test incase it didn't work - which I didnt. I started my pill a few days later and had come close to the end of my packet. About 3-5 days before my packet ended and I was due to start the placebo pills, I began spotting, then it turned into an extremely heavy period. 5 days later, I am still on a very heavy period with bad cramping to where I am sometimes doubled over, and I am clotting quite a lot and earlier I passed what looked like red stringy dry tissue. Any suggestions?