I've had four urine cultures done that come back with wbc and rbc without bacteria. i've had lower back pain and itchiness in vag. what could it be?

Clean catch: It is possible that material from a vaginal infection or inflammation contaminated your urine specimen. Sometimes a catheter is used to avoid that contamination if you can't collect a true clean catch specimen. I suggest that you see a urologist if the urinalysis remains persistently abnormal. I assume your gynecologist has already checked you for a vaginal infection.