Thanks for your query
See i think your symptoms is related to your spray painting and occupation asthma
may be a possibility or there may be chemicals used for painting related chest disorder.
So isuggest you a panel of investigation to reach your diagnosis -
1. chest x-ray PA view
with bronchodialator reversibility on and off your job i.e. donig twice - one while in your job and other while you are away from your job
4. If chest x-ray abnormal then a high-resolution CT scan
) should be done
5. complete hemogram.
Consult a pulmonologist
for getting locally examined and do continue the medications which gave you the comfort.