I'm really concerned because I was a smoker for about 6 years, usually having around 5 cigarettes a day, but I quit almost a year ago because of this upper back pain that's been bothering me. The weird thing is, even after a year, the pain is still there. I've done checkups and seen a number of doctors, but they just tell me it's stress-related and suggest exercise, which hasn't helped at all. Now, for the past 15 days, I've been experiencing breathing issues, like when I take the stairs or even when I'm just sitting or sleeping. The breathing problems come along with the upper back pain. I'm really worried about these symptoms and would love some advice on how to get relief. What could be going on?

do pulmonary function test