Hi sorry for all you are going through. I am not an expert like Mrs D in knowledge but have had so many medical tests basically I was told at Cleveland Clinic I am tested out. Also repeats and have traveled for doctors so can very much relate to the frustration with them. I have a few thoughts
One you have to be very careful in procedure you try. If you go to 4 pain doctors you may get 3 or even 4 different suggestions. Now some are out for the well being of the patient but some will suggest expensive treatments that are not. For me I have done pain relief procedures that actually increased my pain. I guess for my body what was supposed to settle actually revs things up. I know it is a catch 22 because you want relief but it is so important to research and weigh the pros and cons.
In your past can you think of anything that may have happened which you may have brushed off but now may help make a connection? Did you have pneumonia or other similar? Did you get an injury or fall? Any meds you took in the past or other problems?
Hang in there
I wish I could offer more.