Shortness of breathing. And leathery?

Hello I am a 34 yrs old male use to feel only shortness of breathing intermittently that last for few hours or sometimes 1 or 2 days for last 10 years with no h/o cough which subsides automatically . But for last 3 months I m feeling same problem frequently that subsides while taking duty off for 1 or 2 days. I did ECG echocardiograpgh thyroid profile chest x ray spirometry all are normal except xRay Nose and PNS shows right maxillary sinusitis. But most of the time my nose is blocked, so while talking for long for giving lecture I get breathing difficulty and leathergy also. Doctor told me that everything is normal and it may be due to stress of work. Now I m confused whether it's my obsession or really I m having some illness. Kindly tell me what may b the diagnosis and what shud I do? May nasal block be the cause of this breathing difficulty and leathery?