Thanks for writing to us.
Since you have been to doctors and they could not resolve the issue, you seem to be worried. First of all assess yourself that when do you get breathless. If it comes at rest, during period of anxiousness/ stress
but does not come on walking/ running/exercise, it is not likely to be cardiac in origin. If it lasts for few seconds/minutes again it is not likely to be a significant organic problem. But if it comes on exercise/exertion/using stairs/running , is associated with cough/pain chest/ wheeze and it takes a lot of time to resolve, you must see your cardiologist and pulmonologist. Depending upon their assessment, they will advise you appropriate work-up.
Feel free to discuss more.