I am 20 years old. A little over a year ago I went on birth control for nine months. A month before I stopped using bc I started experiencing cramping after I would go running that would last five to ten minutes. After I got off of birth control my period was regular for two cycles but I was still experiencing cramping after running. After two cycles my period stopped, and the pain increased after running to the point that I am throwing up. I am now three months late, but did have what I thought was my period about a month ago, but it did not last a full day. I have been to see the doctor and was given a pregnancy test which was negative and did a pap smear which came back negative for anything. My mother performs ultrasounds and did one to make sure that there weren't any cysts. That was negative and no one has been able to say anything else. I usually don't cramp that badly when I'm having my period and if I do, it's typically every other month, so the doctor said that it probably isn't endometriosis. Anything would be helpful now.