Hello Kajal and thanks for the query
Firstly I want to know your age? If your are around 30, than you must do your stress/ tread mill test to rule out any heart related issue.
or stress can cause this type of attacks. You doctor told you about panic attacks. These are all due to over stress. You yourself can know about how much stress you have.
Do regular exercise, yoga
to reduce your stress.
Finally if you have allergic to some pollen's and you have noticed some substance causing breathlessness than try to protect your self from them.
If you have cough
or any chest pain
than do you chest X-ray and consult your treating doctor.
My advice is to find out the cause and get treated.