UTI is more strongly suggested by the amount of white blood cells present - and at 4-8 WBC this can be suggestive of a UTI. You may also want to ensure that bacteria that grew out was sensitive to the antibiotics you have received.
That being said, you have had a pretty comprehensive urologic evaluation - including ultrasound and cystoscopy, making things like bladder cancer or polyps less likely.
If there is concern about interstitial cystitis, you may want to consider a potassium sensitivity test - which can be discussed with your urologist.
Followup with your personal physician is essential.
This answer is not intended as and does not substitute for medical advice - the information presented is for patient education only. Please see your personal physician for further evaluation of your individual case.
Kevin, M.D.
Medical Weblog:
kevinmd_b