Hi! Your theory about the breathing issues being related to back or rib problems is interesting. I say this because I deal with upper back pain on a daily basis, and when the pain is worse, so is my breathing. Today, for example, I feel so much pain and tension from sleeping poorly, and I’m having a much more difficult time with my breathing than usual. I am in physical therapy for back and shoulder pain, and although the pain hasn't changed much, I do feel that stretching and strengthening the muscles help the breathing a little. It’s also worth mentioning that I’ve been to two chiropractors, but the breathing issue persisted despite several visits.
Also, I sometimes feel some crunching in the area of my ribcage when I move a particular way. This seems strange to me, but my physical therapist didn’t seem too concerned about it, so I’m not quite too sure what to make of that.
Like you, all blood tests and lung function tests came back normal. I also visited a cardiologist and have a follow-up appointment this Wednesday (EKG and stress test were performed). SOB is worse upon exertion, but it’s generally present all the time (even at rest), and some days are better than others.
Because all medical exams have been normal thus far, doctors attribute the SOB to anxiety. To be fair, I am in grad school trying to finish my dissertation, but this breathing issue was present prior to beginning the dissertation process. And back then, the SOB would appear only occasionally (every couple of months or so) and would only get worse when I would go on runs.