What Causes Vaginal Odor Before Menstruation And During Urination?

FOR THE LAST 7 MONTHS RIGHT BEFORE I START MY PERIOD I GET A FISHY ODOR WHEN I WIPE AFTER I URINATE. I HAVE BEEN TO THE OB/GYN AND SHE TESTED TO MAKE SURE IT WAS NOT A YEAST INFECTION. IT WAS NOT. SHE SAID THAT MY PH BALANCE MUST BE OFF. I SHOULD USE REPHRESH AND THE SMELL WILL GO AWAY. WELL EVERY MONTH IT HAS BESIDES NOW. WHAT SHOULD I DO OR BE TESTED FOR? SHOULD I GO TO A DIFFERENT TYPE DR?