What could cause chest muscle soreness after exercise and shortness of breath regularly with a diagnosis of small airway disease (never smoked)?

COPD: You have a form of chronic obstructive pulmonary disease (COPD) which isn't your fault but happens to people from breathing the air we live in and/or second-hand smoke and/or bad luck. See your doctor as there are a variety of inhaler treatments that may very well help you. Be gentle with yourself: you're not 18 anymore. You may need to modify your exercise regimen but exercise is still advised.