Thick brown discharge

I am on my last week of birth control pills for this month. I start a new pack next Wednesday. Today, I woke up and had a thick brown discharge (almost like melted chocolate). Any ideas about what that could mean? I was intimate with my boyfriend about a month ago and we used a condom SOME of the time, but didn't other times. He pulled out each time before ejaculating. Any ideas or suggestions as to what might be happening?