I had similar symptoms when experiencing an anxious period. It has completely gone away now I'm in a better frame of mind ie not worrying.
Take care.
It would not hurt to have an echocardiogram to check your heart valves. It is just an ultrasound of the heart and they also listen to the valves. Otherwise, it could be that you are taking in too much air and causing this feeling like you are not getting enough air when actually you are breathing too heavily. I was doing this for a time because of my allergies. Once I realized what I was doing, I started breathing normal. Are you breathing through your mouth a lot? If you are hyperventilating breathing in a brown bag lunch bag helps. To put your mind at ease and to be on the safe side, have the echocardiogram. My daughter had extreme heart racing when she was only 9, so she had an echocardiogram of the heart and neck and everything was normal. It was a relief being that there is heart disease and congential heart disease on her dad's side.