ladybud

Most likely just because you missed 3 cycles. When that happens, the uterine lining builds up deeply and then you have a heavy often painful period. The grey tissue is what endometrial tissue looks like, it can slough off like in sheets or clumps. Tubal ligation can temporarily put the ovaries in "mild shock" because the blood supply to ovary is interrupted during the procedure. Then ovulation doesn't occur, you miss periods, and this happens (what you are experiencing now). This usually corrects itself within a few months, so this period should get you "cleaned out" and once you start ovulating again, your periods will straighten out.