Bugs are part of life in the woods. Camping may not be for you if you loathe bugs.
That being said, what do you mean "you got invaded last night?" By what??? Mosquitos? Stink bugs? And where are you, South Carolina? Arizona? Florida?
And how did they get inside in such vast numbers that you consider you were invaded?
Do be aware that some places on this continent there are insects that are so pervasive that there is nothing you can do to avoid them except not going there. Mosquitos at the beach, for example. Or stink bugs in the mid-atlantic.
And the latter (just as an example) are pretty much immune to any chemicals that wouldn't kill you, too. All you can do is keep the door and window screens on and hope for the best.
Incidentally, one place flying insects might enter that people don't think about is the stove vent. If the little flap doesn't close completely when the fan is off, the'll fly right in, there being no screen there.