Thanks for your query.
I think you had asthma
in the past which has gone away but just before your exam as you are in tension, your anxiety
has provoked it a bit but i am not sure of it whether it was an asthma episode or else. For it you need to undergo some investigations -
and bronchodialator reversibility
3. chest x-ray
I suggest you to consult a pulmonologist
and get yourself examined.
Because asthma is diagnosed mainly clinically and confirmed by spirometry finding. I think you got my point.