Momma, i can only believe its related to the intense hallucinations/dreams.
are you having extra cataplexy? are you exhausted or extra stressed?
i notice heartburn (on a scale from mild to reflux) is often different for me if im having C.
also, that heaving/gagging can be a "twitch" in the diaphragm, and C suppresses breathing for me. you could be getting into an HH zone during sleep, where you begin to struggle for breath.
and (just flying wild guesses here) i get spinning vertigo even lying down sometimes, and that is a bit barfy.
try to change something about your sleep: soft music/ complete quiet, soft light/heavy drapery, whatever is a change. maybe you can get around the disturbing gagging by controlling dreams, for now.
i sure hope the sleep labs open up diagnosis and treatment for you, you have suffered too long.