As well as Gatroparesis you could consider having a H.pylori test. This is a very common gut bacteria that causes burning stomach, heart burn, slow digestion. Also belching especially if your glucose is high and the bacteria have a fart party.
Some centres can use a breath test; most need a stool sample. Results typically in 3 days and a week of strong antibiotics will fix you. Although perhaps wait for COVID 19 to pass so you don’t become immune suppressed.
This bacteria is also associated to digestive track cancers so it best to rule it out. And if one person in your household has it then everyone should get checked.
Finally make sure you take probiotics after treatment to restore the good bugs and improve your immune defences.