TMI: period help??

Usually have bad periods but I started today and I have been cramping for weeks now and having nausea and very emotional. Anyway, my period is usually heavy and consistent. Right now it's all clots. And I just checked and I had a clot about the size of a quarter and beforehand I was having TERRIBLE pains that I couldn't even breathe with. The clot had tissue in it and honestly (this is gross I'm sorry) but looked like the texture of shrimp, what could it be?