What Causes Brown Vaginal Discharge Post Menstrual Cycle?

Hello, I have a question earlier this month on the fourth I started my period. It lasted for about 4 days before it turned into a dark brown spotting that lasted until the fifteenth. Then on the twenty-sixth I started to spot a dark brown discharge that has gradually gotten a little lighter but I still have it today which is the twenty nineth. I was wondering what you might think it is? Please note I have pcos, the discharge is odorless and there is a slight pressure in my pelvis. Thank you for your time.