stomach, esophagus, para esophageal hernia caused by, (stomach
being shoved up into the chest
due to be over weight, wearing belts or wastebands to tight, coughing to hard or to much, seizures), vegus nerve, gastro-paresis( suggish or paralized stomach)(very common ailment causes by diabetes, meds, surgery, aging). etc.
The best thing to do is to do a complete blood workup, endoscopy/colonoscopy, and get your heart checked. These are for starters. Then go from there.