You are one of those with high mucus in respiratory tract. Not only nose felt block and lung not inhaling enough air/oxygen

Body can produce excessive mucus because of virus, pollen or eve dust in the air. I bet you felt better in warm environment or even just when taking hot beverage.

Perhaps just keep body warm. Increase air-cond temp. Buy air filter but the filtering material can be expensive to maintain, or maybe buy ionizer. Ionizer help settle dust to the floor instead of floating around in the air very long.