What Causes Brown Discharge And Headache After Periods While On Micronor?

Hello.I've been on micronor birth control since September and it's been great until last month when I recieved my period at a normal time and then 4 days later I recieved it again. I'm 19 years old. Now I just finished my period it came at a normal time but lasted for about 10 days as opposed to 6 as per usual. Now 4 days after my period ended im getting brown discharge and a lot of it.With this brown discharge im also getting headaches.This is the third pill I've tried. Any suggestions ?