Recurrent kidney infections usually require a workup to look for stones, and/or abnormal kidney and/or bladder anatomy. This is probably best done by a urologist specializing in female problems. The back pain may be related to trigger points in the back, abdominal, and/or pelvic florr muscles. This is probably best evaluated by a physician specializing in musculoskeletal problems (This is usually a physiatrist, not to be confused with psychiatrist - who specializes in mental illness). You will be in a better position to know what to expect after evaluation by both specialists.