What Was The Skin Like Discharge During Menstruation?

Hi, a ball of skin like material came out during my period. It was the size of a 50p peice. There was little blood it didnt look like a blood clot to be as it looked more like skin. I dont know if it is related but my periods have suddely become painfull over the last six months and my doctor told me to just combine my pills and not have so many periods. I havent done this as i dont feel right not having periods. I'm worried there is something more serious happening now.