You could be suffering from chronic obstructive pulmonary disease like bronchitis or emphysema, heart attacks, strokes,
cancer oral cavity and
cancer lung. Consult a physician for the needful assessment so that any serious illness is screened and caught early for prompt management. Investigation would include chest xray or CT chest, blood tests, arterial blood gas analysis,spirometry, ecg, echo, assessment of effort tolerance. Hope this helps. Take care.