Have you tried an allergy testing, it's amazing what it can pick up. I think Holland & Barrett used to do them, but if not I am sure your doctor can refer you to someone, if not, perhaps try a homeopathic practitioner or acupuncture. I swear by the latter as it cured me of a 20 year plus back pain problem! Failing that a friend of mine many years ago, used to have to sit in a bath of potassium permanganate crystals to cure the same problem, but not sure how it would fare now! Good luck.