What Causes Brown Vaginal Discharge During Periods?

Hello, I am 38 yr old, I am 192 pounds. I have 3 children my youngest is 12 years old and I had my tubes cut during my c-section. In the last 2 years I have been trying to have a baby, starting with a failed tubal reversal, two failed IVFs my last one in Oct/Nov 2011 which ended because I was bleeding 3days after my ET. But before we started IVF, my RE did a hysteroscopy to insure my uterus was healthly and he said he found one pullip and removed and said my uterus was healhy to proceed with IVF but I bleed. Now my last few menstral cycles I have a brown discharge that continues 5-7 after it has ended. What does this mean?