Im nineteen years old. I haven't had a regular period since December 22, of last year. I had unprotected sex on January one. Missed my next period. I then took a pregnancy test. It came up negative. Its now middle of March and I still haven't had a period. HOwever, I've had brown mucus like discharge almost every two weeks.. Its mostly when I wipe, but sometimes its on my panties. I've taken about six pregnancy tests since January and they have all been negative. What could this be?