What Causes Brown Vaginal Discharge Until I Ovulate?

I had a tubal ligation 9 years ago. For years now I get my period and then proceed to have a brown vaginal discharge until I ovulate. Once I ovulate I go back to normal and no more discharge. This was driving me crazy having this discharge for 2 weeks. My OBGYN put me this month on the pill to see if it helps. I've been on the pill for 15 days now and I still am having a light discharge...when I wipe the toilet paper has the brown discharge. My concern is how can being on the pill help when now I'm not ovulating and usually this discharge stops once I ovulate. Is this the correct way to help solve my problem?