I have recently (the past 4 days) had a dark brown discharge (sometimes light, sometimes more mucus-y) and slight cramps. My period was 2 weeks ago approximately, and isn't due for another 2 weeks. Usually I get this a little under a week before my period, so this is abnormal to me. I am on birth control but have been for a little over a year, so this shouldn't be the cause. I had sex a day before this discharge began, and that's it since my last period. What would be causing this?