Male w/ 1/12 urethritis symptoms. since then i have had 2 x negative sti tests with ct and ultrasound also -ve. symptoms ongoing. 1st uc was taken 1 hour post urination and 2nd whilst taking trimethaprim. chance of 2 x false negative results?

More info needed. What symptoms? Why CT and ultrasound? They cannot diagnose urethritis -- maybe actually a prostate problem? Trimethoprim isn't available in the US; maybe sulfa-trimethoprim (Bactrim)? That antibiotic doesn't treat urethritis. Have you also been tested for UTI bacteria? Or for Mycoplasma genitalium? Ask a clearer question and maybe we can help. But it seems no urethritis at all.

Your question has too many confusing things. Urethritis is a diagnosis. What were your symptoms? Why so many expensive tests and of what area?. Chances of two successive urine cultures being neg with an infection are near )0. You should see a Urologist who listens to your symptoms then physically examines you. In the meantime drink water and avoid alcohol .Good luck