3yr old spayed female, is having a vaginal discharge, brownish in color, foul odor. Vet treated her with Batril for a week, then two weeks, still no change, and the area of the opening became swelled and lumpy. She was then treated in the hospital, I think with injections, and higher dosages of Batril, and she seemed healed, but after about two weeks she has started the discharge again. The vet thinks it is because she is fat and unable to clean herself, but I have wached her clean the area, so she can reach it. They also shaved the hair around the opening. What could this be?