I have small (less than 1cm) bits of tissue coming out of me along with small blood clots and the regular blood, for three cycles now. It doesn't look like a uterine cast and doesn't have the characteristic "chicken skin" appearance of endometrial chunks. I have had negative pregnancy test results. It is not mucus - I can't pull it apart and it does not dissolve in water. The doctor doesn't know what it is. It looks pinkish whitish. Has anyone had this? Do they know what it could be?