what can cause frequent urination? tests for diabetes and infection were clear

i started noticing in November that i seemed to have to urinate more frequently, especially when i went to bed-tried to fall asleep. it wasn't so much that i would fall asleep then wake up to go but rather I'd have a strong urge to go, then urinate, go back to bed, and either immediately or within 30 I'd get the urge to go again. it seemed like i would have to go like 6 times a night

went to normal primary doctor who tested for diabetes and infection, both came back negative, so they prescribed Tolterodine (detrol), which after a month or so seemed to have little to no effect. they then referred me to a urologist at a mens health clinic.

they had me urinate into special toilet-machine to measure flow, did the light shine-scope on testicles, and scan bladder.on different day had me go to radiology for full on ultrasound of testicles. and they had me complete diary ie pee chart

nothing on scans, overall volume in normal range, frequency overall abnormal 9-14 times, per void wide range largest 20ish ounces, other times low 2 or less.

put me on flomax to try level them out. i didn't feel like they really had any answers especially when they said part of it was behavioral.overall its quite annoying. after a bit now its causing stress and anxiety as it relates to social life and job hunt future in general.

any ideas what it could be? is it rare for someone my age to get? i know anxiety and stress an CAUSE bladder-urinary issues but does it work the other way around?