I was actually wondering the same thing. I was on Birth Control when I went to visit my boyfriend for a week and about 2 weeks after returning home I got mega-bad cramping. I had some spotting that day and the next and thought it was weird but then when it came time for my period it was a few days later than normal and again I had some cramping which is abnormal for me since I had children. One day on my pad I had what looked like an approximately 1 inch light greyish colored deflated ball with a tail of about 2 inches. Then, when I wiped I had another thick 2-3 inch long piece of what appeared to be tissue. I'm not sure what all this was and was hoping to find an answer here but it seems there are many people asking this same question and no one answering it. I havn't gone to the doctor and don't think I will unless I feel ill. If anyone else has had a similar experience please let me know.