What Causes Abdominal Pain And A Brown Discharge?

Hi, I am a 19 year old girl who has never been sexually active. I have had a history of ovarian cysts and have been placed on Seasonale so I won't have a period every month. I shouldn't have a period for another 2 months, however, I have had sever lower abdominal pain, nausea, back pain, and what started out a a little blood is now a brown discharge. I had an ultrasound yesterday but everything came back normal. What could this be and what should I do?