I will add to this as I go along but thought it may be useful for some members:
You cannot breathe and swallow at the same time (as the same airway/tube is used) so when you try to swallow and feel that you can't breathe in - this is why.
One takes precedence over the other but please be reassured that you can do both within seconds of each other so you won't stop swallowing or breathing though it may feel like it.
You may experience this when eating and you swallow and then seem to gasp for breathe - this is why. One thing has to act before the next one and it can feel like you can't breathe and/or swallow but please be reassured that you can.