Talk to Pulmonologist / Lung on Respiratory System

Sir when i go to the Heavy crowd place like going to Jumma tul Mubarak Prayer in Mosque( in standing position only ) I felt there is trouble in breathing and I cannot breath with nose and I start breathing with mouth very fastly anr deeply. During my stay in this heavy crowd place I felt that i oxygen level in blood is low due to which I felt breathing difficulty. When I come out of the Mosque/heavy crowd place my breathing becomes normal and I felt no trouble. This trouble happens only when i am in heavy crowd place like Mosque in standing position only. I don't know either it is due to mucus in my lungs or due to heart short blood supply to body during this. Also This thing happens to only me rest all the other persons remain normal. Kindly tell me its treatment without appointment as I am a student. please thanks