Hi Sammy,
It’s not uncommon to experience all sorts of strange spotting, discharge or change in the way your period looks after you start taking the birth control pills. What you're experiencing now - a dark brown discharge - is most likely your 'leftover' menstrual blood. It's colored this way because the longer the blood stays in your uterus or vaginal canal it gets darker. It's also quite possible that this brown discharge might be caused by birth control pill hormones stopping your ovulation. Since everyone is different, the pill hormones probably will have this effect just this month and things will get back in order in the next week or two. Just make sure you're taking the pills at the same time each day (+/- few minutes) - that's the most important factor that contributes to breakthrough bleeding when you're on birth control pills.