For info, most people with tmau also have candida,
Both of these conditions are affected by diet.
If you constantly have a fishy odour, then you need to go to your GP and ask to be tested for tmau. If the odour is only coming from your vagina, then it is possible it could be BV, however, I would be suprised if BV reduced with diet as it is a bacterial infection in your vagina.
It sounds more like tmau, however, no-one can guess what your problem is so you need to get tested.