Am I having a miscarriage?

I don't know if I was officially regnant but I did have unprotected sex a few weeks ago. I was patiently waiting for my Period. I started bleeding Sunday so I assumed it's my Period. I started out bleeding normally than whoosh soo much blood. I been having rock size clots coming out of me and extreme abdominal pain. During my regular eriods my flow is light and I have no cramps. This way different I had to take off work and skip class. What should I do I'm worried?