Gag reflex so bad a dentist idk if I’ll be able to handle going. Help

I’ve always had a sensitive gag reflex but it’s gotten worse of the year. Maybe do to my acid reflux idk. I also have positional vertigo so lying way back in a chair while someone putting things in my mouth is a bad mix. Last time I was there it was so bad I left early. I’m not sure what to do because I want to check up on my teeth but I don’t want to be horribly sick. Any advice.