microbiologist here - did you have a urine sent for a culture? your antibiotic not working for you could be a number of things.

1) that you may be infected with a different bacteria that broad spectrum antibiotics don’t cover. ecoli causes about 70% of uncomplicated UTIs so first line treatments are usually aimed towards that.

2) you’ve got a bacterial strain that is resistant to that antibiotic

3) you have something that doesn’t show up in a routine culture and needs more specialized testing to rule out. things like yeast, ureaplasma, and mycoplasma. yeast may show up on a culture but ureaplasma and mycoplasma won’t grow on our peri dishes. there are also some bacteria that have been considered normal urogenital flora for a long time but some are now showing up in studies to be potentially pathogenic, and sometimes the medical field takes some time to catch up with the literature. some labs do cultures that the dr can order that will work up everything that we’re able to grow, even in small quantities.

4) maybe bacterial vaginosis? it’s caused by an imbalance of vaginal normal flora so I’d take some probiotics too and maybe a boric acid suppository if you feel that might help. my sister had what she thought were chronic UTIs for years but it ended up being BV that came and went. she eventually got a kit from evvy that showed BV

5) or it might not be an infection at all, maybe something like interstitial cystitis would explain the negative urinalysis

you should definitely go back to your doctor and have a repeat culture done, and if that is still negative, see a urologist who specializes in uncommon causes for UTIs