What Causes Brownish Discharge During Menstruation?

I was taking Levest 150/30, I stopped for a month then resumed. I took it for 3 weeks but I haven't had a proper period only brown discharge. I started taking Microgynon the day I was due to start my new packet but that was a day after the brown discharge started. I haven't had a proper period is this because I stopped and then restarted taking Levest or is it possibly due to starting to take the Microgynon?