Constant blocked nose, postnasal drip and short of breath after light excercise and sometimes when sitting, also suffer from anxiety. what could it be?

Anxeity ; Breathing: Sounds like a chicken ; egg situation. Blocked nose and breathing issues can make us anxious and being anxious can make us feel like we are short of breath. Check w/your doc to get the blocked nose cleared up and if the anxiety continues a clinical psychologist can be of help. I see that your tobacco use is 0-2 packs a month. Freeing yourself of smoking entirely will be a plus in many way.