What Causes Brownish Discharge After Taking Birth Control Pill?

I was on birth control for less than one month. My cycle returned the following moth for the normal time it normally is about 6 days. It started off with a brownish discharge 2 days then began it s normal flow for the next couple days. The following month I had the brownish discharge for about 3 days and then my normal period for an additional 7 days. Longer than I am used to. This month my menstrual cycle started with this dark brownish discharge for about 6 days now and has not changed. My flow normally started off light the first day, heavy red flow with intense cramps for about 3days and then light to end off the last 2 days, before birth control. I find that my flow is no where close to what I m used to be and I have no cramps. It is non existent in the night and early morning. Probably have to change a pad or tampon once for 2 of these days and it is not saturated. Should I be concerned.