Hi Hattie, I have the same problem and have browsed through the net briefly searching for an answer. My first theory was that maybe it is a left over from my period and it just finds its way out later. After reading other people's stories i noticed we had some things we had in common. Most of us either have been diagnosed with endometriosis or suspect we have it.   I suggest you go to the doctor if you havent already because your reproductive health is very important and quite a delicate thing. You may expect tests that include pap-smears and an ultrasound. None of which is painful if that is what you are worried about.   All the best