Brief Answer:
Doesn't appear to be any serious problem

Detailed Answer:
hello,
Most likely this is psychological problems since only psychological causes will improve will exercises and also your age is not compatible and don't have other symptoms of any organic disease.
Usual causes of shortness of breath, includes anxiety, acid reflux, heart and lungs diseases.
Do you have any stress, weird thinking, increase in shortness of breath on particular thinking, insomnia etc if yes it supports the anxiety as a cause, and you need to either try relaxation techniques like deep breathing and yoga for this and if doesn't help you can anti anxiety medication like tab ciplar LA 20 mg prescribed from doctor.
I guess you don't smoke, don't have any wheezing, cough with sputum production, ruling out lungs problem, if yes you could have chest x-ray.
Do you have any palpitations, bluish discoloration of fingers, chest pain, history of recurrent lungs infection, if yes you will need echo.
It can be a acidity and reflux disease. Do you upper abdominal pain, nausea, bloating, burping, increase in pain on food, sour water feeling in throat or chest burning, if yes it suggests.
In a nutshell, it doesn't appears to serious condition, but still one chest X-ray, hemoglobin, echo can be done if symptoms persist. Avoid smoking and also alcohol if any. So get back if you have some more doubts and information about your problem.

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