What Causes Dark Brown Discharge?

Hi I am 2 months postpartum, I bleed the first week and a half stopped then had what I thought a normal period for me lasting 3 days and a normal dark red-red color. Yesterday I started having a very reddish brown to dark brown discharge. It doesn t have a foul odor and hasn t filled up more than 2 tampons though I am still changing them every 6-8 hours. My doctor says that everything is cleaned up inside and is healed correctly so I am confused on what this brown discharge is.