Never Ending Period

My period was late but I haven't had sex in 5 months, long distance relationship. I've been stressing horribly going to school full time and working 2 jobs. I thought I was pregnant took a test and it said it was negative. So my period finally started and now we're on day 10 of this yucky brown discharge that's been happening ever since day 6. Help!!! What's going on?? What did I do wrong?? What is it?? Oh and I started my birth control the day I started my period.