Re: Breathing hurts lower back
If you failed your lung function tests, your lungs are not normal. They are not functioning properly and now you need to find out why. Is it the lungs themselves or the pleura that are the exterior lining of the lungs. Pleural fibrosis can make it hard and painful to breathe(many causes). Heart problems can cause the lungs to not function right if they aren't getting enough blood to carry the O2. You didn't say which side of your back but if I remember from another post, it's the right side. Not much else there except the liver below the lung but lung pain can appear all over the place. Just ask anyone whose had pneumonia.
Now that you've ruled out your spine, follow up with the pulmonologist and see where that leads. Someone will figure this out sooner or later. I'm in the same boat and I think I may have found a clue to my problems last week so I'm off hunting again. It takes time and patience but it's better than sitting at home waiting for the worst.
good luck again................Jenny