I don't think with only bad breath you can have TMAU, primary TMAU is genetic and genuine cases usually smell strongly of fish from a young age.
For BB try using hydrogen peroxide diluted with water (otherwise it will burn your skin badly look into dosage) as a mouth wash. Baking soda could help also.
Bad breath could be liver toxicity or Candida if you have a white coating on the tongue.
I expect you have probably been to a dentist to check you don't have an abscess or gum disease.