youre not alone, i had the same problem a couple of years ago. i had the same foul odor... to me it wasnt fishy, it was much worse. it was accompanied by kind of greenish vaginal discharge. went to the doctor and they said i had BV.
What did the doctor test you for -- have you been tested for BV, or just yeast infection? A hallmark of bacterial vaginitis is a smell usually called "foul" in the medical literature. If you know for sure you have been tested for it, then you might talk to the doc about other possible reasons, such as a diseased internal organ. But it frankly sounds more like it's BV.