When I was passing clots like that...and some looked like I had passed my whole liver!!!...I had fibroids. This was also accompanied by very heavy bleeding. An ultrasound confirmed my diagnosis, and since I had the fibroids removed (myomectomy), I have not had the large clots or extreme bleeding that I had before my surgery. I am now perimenopausal...complete with somewhat unpredictable periods, some light, some heavier, some small clots...but nothing like I had before the fibroids were removed. If I were you, I would get it checked out.