What Causes Light Spotting Followed By Sudden Discharge Of Blood With Clots?

on tues when i went to the bathroom and wiped myself i noticed a very pale redish color on the piece of toilet paper then later on in the evening it got darker. I had severe cramping all night, worse then i have ever had and painkillers didnt help so i layed on a heating pad all night. Wed i had heavy bleeding then again severe cramping all night so again im on a heating pad all night, This morning i got up at 230am for work and had a shower. i put a tampon in and about 20 mins later went pee. Blood came out almost like i was peeing and several blood clots. When i wiped myself i had something that was a pale red looking jellyfish that was almost the size of my palm. I thought i had forgotten to put a tampon in but then realized i hadnt and all that came out through a tampon. I bled through several tampons in about 20 min periods. I now have no blood but still have really bad cramping. I normally have problems pulling them out so i dont know how all of this came out around one. Thanks