Shortness of Breadth can be of many causes
That include cardiac or pulmonary
You should have complete workup for that. Workup includes Chest Xray an EKG and Echo.
To rule out the serious things.
It can be due to Asthma
if you have these entities must visit your physician and have treatment for the true diagnosis.
I hope I am sucessful in solving your query I you have more you can ask me
Dr. Azhar Sattar