UTI and Kidney Infection Wont Go Away?

Has this happened to anyone? I have symptoms of burning urine and back pain; but blood, urine and radiology tests all show no infection. I have had the kidney infection for 3 weeks and the UTI for over 2 months. Been on 7 different antibiotics, UTI got better for a bit but back pain still there. Doctors just giving me pain relievers, don't know what to do.