help!!!!! lots of blood clumps

I started my period around 7pm on October 4th. I have been experiencing extreme cramps and their is a lot of blood clumps. I'm bleeding a lot. I have never once bleed this much or had this much pain on the day my period started. I didn't experience any cramps or any pmsing before my period started like normal. I've been sweating really really bad. I took some midol because it helped the last time I had my period. But this is unnatural. My periods are on a schedule. I don't know what is going on. Why is this happening?!!!