definetly see a doctor first to rule out anything more serious... or possibly if it's allergies
it sounds like hyperventilation - usually when you think about your breathing you breathe far too much - and this leads to over-breathing and all the anxiety, feeling like you can't take a deep breath, etc.
the old way to treat this was to breathe into a paper bag - but this can be a little unsafe... you can instead breathe slowly and relaxed into your hands cupped over your mouth and nose, or breathe into a sweater/shirt... just helps get the CO2 back up
CO2 and oxygen have to be in balance for the lungs and aerobic system to function properly
if you've been overbreathing for a long time, sometimes tired respiratory muscles can you feel short of breath when you laugh/shout/talk - very common in actors and singers...
really you need to set aside a few times a day to lie down and exhail completely by relaxing your lungs... wait until the urge to breathe in again and let your lungs breathe themselves with minimal exertion... there's a physiological breathing reflex you need to engage