I am really sorry for you. I don't understand why the doctors don't do more tests, don't search for the cause.
You've probably tried it already; but I read about turmeric helping folks with MRSA. You can check this on Earth Clinic. You might try "golden paste", which is turmeric with some other spices and coconut oil etc. I take it in mashed up avocado. You must add black pepper to make it bioavailable internally. You can use it topically also.