I dont know if you have been following my recent posts about my daughter (7 yr old salt wasting, born severely verilized, corrective surgery age 2) but she has recently had  problems with low pelvic pain and they kept thinking she had a urinary tract infection or bladder or even a kidney problem but no dice.  Every catch was clean and would come back negative for infection but her pain continues.  I dont know about your daughter but mine has an extremely high threshold for pain so to hear her cry  like this is not only new for us but its quite sad.  This past two weeks she had an ultrasound and a sonogram.  They have found that her bladder is not emptying completely.  She will be seeing a urologist on Thursday.  It would be far fetched if your troubles are the same but something to mention to your dr's.  They say she may have built up scar tissue near the urethra from her surgery a few years ago.  I will definitely let you know.  Look for my posts late Thursday or Friday.  Good luck to you.