I took the single dose to treat trichomoniasis 3 days ago, my symptoms are still very persistent. should i be concerned?

Return to doctor: Single dose metronidazole (or tinidazole) is pretty good but not perfect. It works 90% of the time, i.e. there's a 1 in 10 chance treatment will fail. Also, trich can be confused with or accompanied by bacterial vaginosis, which requires treatment for a week. And other STDs, especially gonorrhea or chlamydia, often go along with trich. Return to doc or clinic to be checked for all these.