What Causes Brown Vaginal Discharge While On Crimson And Ensoft?

Hi Doctor,

I am 25 years old and last month I visited a doctor since my periods were one week early from 6 months. Doctor has prescribed me crimson, ensoft medicines. Its been one month I started using them and this month at the time of my period I observe dark brown discharge instead of red blood. I get this from 2 days which is very less and had a very bad leg pain and headache. What could be the reason