Hi,
You definately need to see your Doctor, many things could be causing this. I had Endometriosis and fibroids in my uterus and was in horrible pain, I was also having the large clots you mentioned and was doubled over . Good luck and I hope you get this sorted out soon.
Angie
Go see your doc. Hard to judge, maybe you have a uterine polyp. You need diagnosis rather than suggestions.