Just Walking A Short Distance, Not Every Day, I Feel

Just walking a short distance, not every day, I feel I have to take short quick breaths to get my wind back. Also at night while lying down I wake myself coughing. I have no allergies I know of. I do take blood pressure medicine. I am 70 and overweight but not obese. Any answers? Also during the day I sometimes have a dry cough with nothing coughing up.