I have tough, membraneous, tissue- like discharge during period. What is it? I am on the pill but started my pack a week late this month.

Uterine lining. Each month, the lining of your uterus which is made up of 'mebraneous material" grows in response to hormonal stimulation preparing for possible implantation/pregnancy. If no pregnancy occurs, this lining is shedded (because of drop in hormones (estrogen, progesterone) at end of cycle resulting in menstrual flow and thus you see the "membraneous tissue." hope that makes sense. Have fun learning.