I am not an expert but biofeedback when I did at Cleveland Clinic and on my own with a therapist was used to help relax ones body, muscle tension, and temp control. All of which can help you either cope with your condition. Also when more relaxed and controlling your body it can in turn help pain. Or it can help other items such as sleep and digestion which in turn can help pain. This was similar of what I was told about acupuncture.
I just don't get how it would be used as dx but I could be wrong. You still may want to give it a try. It is expensive though if insurance does not cover