So I've been pretty sedentary during the last three months and during the processing gained about 15 pounds. I just went on a run with my dog who is very quick going up and downhill and my chest was tight in the middle without pain and was short of breath. I had a ECG and chest x ray last week that's ca,e back clear , am I just out of shape? I've become overweight and this was my first time running in three months