The amount of bugs that you eat or swallow while you sleep is most likely 0 bugs or insects most of the time.
It is possible to swallow or eat bugs while you sleep but the bugs would be small bugs that you likely cannot see.
It's a myth that we swallow spiders, roaches, mosquitoes, flies etc crawl into your mouth and then you eat them while asleep.
Spiders and other insects would not want to crawl into your mouth to be eaten so they avoid your mouth at night.
The insects and spiders may crawl on you while asleep but you'll usually feel them doing so and if you're not a very sound sleeper you might wake up.
But you do not swallow or eat much if any insects or bugs while you are asleep.