What Causes Passage Of Skin Tissue Through Vagina?

i came of the depo in jan after having 1 injection. for months i have had iregular bleeding then this month i am on a 28day cycle but yesterday i noticed a peice of skin like thing come away when i was on the toilet. i have a very small cyst on my left ovarie are these linked thanx i am 33 5 foot 5 and just over eight stone ...i had a loop biopsey in 2002 and my last smear came back clear