I need some personal help

I've come here because idk where else to turn to. I've had an ongoing problem for over four months. It started with a uti and that went away but I still feel the need to urinate frequently (every hour and two or three times during night) however hardly any urine is passed. I've had all cultures everything in my urine is normal. Had Cystoscopy done and all dr could say was my urethra was narrow, dilated me, didn't work, put me on Ditropan, didn't work. I had an ultrasound done and it should I have a post void residual volume of 250ml. I believe? I had a baby almost nine months ago if that helps, and started birth control pills two months prior to this starting first time I was ever on any form of bc. I'm losing my patience and I feel like my dr is very rude and not doing a great job, does anyone have any ideas as to what could be causing this?

TIA sorry this is soo long.