Hello..I'm 25 Years Old & I Have One Child And

Hello..I'm 25 years old & I have one child and Since he's been born I have only had sex with females. My cycle is pretty irregular but lately it has been coming every month. This last month it came for 6 days and was gone on the 7th as normal but about 5 days afterwards I starting getting a brownish discharge almost everyday. I also noticed that I have been get I g headaches since the discharging started. I'm not sure what could be the cause of this. What should I do?