I'm in a similar situation - and I also apologize for the length of my post, but everyone seems to think your whole background is important.
I am 22, I have been sexually active since 18 and on the pill constantly since 17. I do have a current sexual partner; we always use condoms. I've always been prone to yeast infections.
The recent history is that for the past few months, I kept getting my period earlier and earlier, so a month ago I decided, "I'm going to go off my pills for the rest of the pack, let my body have its period whenever it pleases, and then start the new pack when I normally would have." My period started immediately and went normally, but since then (3 weeks) I have had this brown discharge! Like the above poster, it is dark brown, almost black, not sticky or clumpy, odorless, although I am having a bit of itchiness (however, given my history with yeast infections, I suspect this to be from wearing pantyliners for a month straight).
I would believe that it was blood, but I would be extremely surprised if this was pregnancy-related; is it possible that my body has all this built-up old blood that the Pill was preventing from escaping, and that's all this is?