What Is The Treatment For Lower Back And Pelvic Pain?

I have had 4 consecutive urine tests that show trace protein and WBC present. I also had RBC present (last test was negative for RBC), did a course of Cipro, but culture taken before I started taking it came back negative for bacteria. I also have flank pain, low back/pelvic pain that radiates into my left hip (excruciating at times). CT scan did not show anything remarkable. What could be wrong?