Hi!
If you were my patient, I would start by checking for any type of infection of the uterus, including STDs. I would probably also want to do an ultrasound, and some hormone levels such as thyroid and prolactin. Depending upon the results, I would want to figure out some way to reduce the amount of blood loss with your periods. Sometimes something as simple as Ibuprofen can help (taken properly it reduces blood loss). Other options include oral contraceptives or the Mirena IUD. If you don't want more children, you might be a candidate for an endometrial ablation, or even the ultimate--hysterectomy. You will most likely need to visit your doctor to get this sorted out though.
Good luck!
Dr B
I had horrible clots - almost satsuma sized which just started out of the blue. Found out had become hypothyroid - once I started on replacement hormones the problem resolved, no more huge clots and am gradually returning to a normal level of blood loss.