I have a fishy and sometimes ammonia vaginal odor. had tests done for bv, trichomoniasis, and yeast. all negative. can these tests show a false positive? what else causes these issues besides infection?

Consider rechecking for bacterial vaginosis and trichomoniasis, which are the two main causes of fishy vaginal odor. (Yeast infections generally do not cause significant odor.) Make sure you are tested for trichomonas DNA (i.e. PCR test). Other tests for trich, like culture or microscopy, are frequently false negative, missing up to half of all infections, whereas PCR detects all infections.