@DogLover I agree with @vdm, you might have Vagus and Carotid irritation along with Jugular Vein compression based on your symptoms. All these three run in the same Carotid Sheath so it is likely that you have irritation all of them causing these symptoms when upright. See the symtoms list from Carotid and Vagus irritation and see how it resembles yours.
Source : https://emergeortho.com/wp-content/uploads/2018/04/1-s2.0-S2468781220301399-main-2.pdf
It was also posted here in the research area by Andrea who I believe co-wrote this study.