I had thoracic outlet syndrome surgery on April 8th. I also am having difficulty breathing deeply. I only mention this since you also had surgery on your thoracic area. I can feel the problem is from my right lung which is the side where I had the surgery. I have read that during the surgery, air can get trapped between the skin and the lung whiich can cause discomfort and in rare cases a collapsed lung. Mine is finally starting to improve after 10 weeks. Try some deep breathing exercises and diaphragm breathing. Good luck!