I just wanted to add a couple of things. I know nothing about the lung condition. Did you notice how low your B12 was? Did the doctor say if you should take Sublingual, instead of regular tablets? I ask that, because some people don’t absorb it well, so injections and sublingual are the only options. B12 deficiency can cause significant fatigue. I had it and many symptoms relieved after months of treatment.

Did they check your thyroid? Hypothyroidism can cause severe fatigue. Mine is treated and I no longer have fatigue.