Blocked nose & headache on forehead occasionally,mucus stuck in throat,no cough,feeling breathless once a while, how to confirm whether i have asthma?

Sinusitis: But to be sure have somebody listen to your lungs for wheezing

Asthma : Studies show asthma is sometimes a misdiagnosis. The diagnosis is confirmed with a test called spirometry where you breathe into a machine then we see if a bronchodilator overcomes an obstructive breathing pattern if present. Asthma is an obstructive lung disease. https://www.aaaai.org/conditions-and-treatments/conditions-dictionary/spirometry