What Causes Foul Vaginal Discharge Inspite Of Having Bacterial Vaginosis?

Hello, I m 39 years old. I have had BV on and off for 6 years now. This is driving me crazy. I am currently being treated with metronidazole pills. I have been taking the medicine twice a day for six days. Today I am still having a discharge, now with a rotten egg smell. What is this? Is this normal?