Bleeding in the middle of birth control pack?

I've been taking Tri-Previfem birth control pills for about 6 months now and have never had any problems with it; my period always came on a certain day, no spotting, etc. Today I went to the bathroom and when I wiped there was dark red/brownish blood or maybe discharge. I'm in the second week of my birth control pack so I know it can't be my period. I last had sex on Friday, and he didn't "go" inside me and I also have no other pregnancy symptoms so I'm not too worried about that either (plus it's too early to tell). I'm just wondering what this could be since I've never experienced it before. I always take my pill on time (sometimes 10-15 minutes late) but it's always around the same time. Any answers are appreciated!