I went to an STD clinic 9 days ago (the day after the symptoms recurred, following sex), where I tested negative for gonorrhea. They also took tests for
chlamydia and syphilis (not related to the burning, but their general policy), which still haven't been come back yet. They went ahead and gave me single-dose blasts of metronidazole (aka flagyl) for the possibility of trichomoniasis, and azithromycin for the possibility of chlamydia.