I can understand your concerns and would try my best to address them.
Generally stomach pain and a gag kind of reflex in the throat comes due to reflux gastritis and gastric ulcer. This pain is most prominent after or during eating and may also come when your stomach is empty. Often this is accompanied by gas in the gut and hence, you feel shifting pain.
Gas can also be due to excess consumption of food rich in sulfites like juices, molasses, yellow dye in ready made food stuffs, and red wine. Sulfites are present in lesser amounts in mashed potatoes made from dry powder, pickles, tinned shrimp, cookies, crackers, and readymade pie dough. So, check and see if you consume too much of these.
Endoscopy is the right approach to diagnosis and the doctor may spot inflammation or ulcer of the gastric mucosa. This is usually caused by H pylori infection, and in your case you are tested negative for it. However, the possibility of H pylori infection increases since you have enlarged mesenteric lymph nodes usually caused by Helicobacter jejunitis, This is also often the cause of abdominal pain. So, you should be re-tested for H pylori infection. Generally treatment with antibiotics and probiotics are enough to take care of this.
You will need to take a combination of medications (under medical supervision) like a proton pump inhibitor such as omeprazole, lansoprazole or pantoprazole empty stomach in the morning and an antacid gel after meals or H-2 blocker such as ranitidine for complete relief.
Also you need to make some life style changes such as taking a late night snack, drinking cold milk, avoiding heavy meals and eating frequent small meals, avoiding too much of caffeine, tea, smoking, fried food and drinks both alcoholic and non alcoholic fuzzy ones, avoiding heavy exercises within 4 hours of a heavy meal, raising the head end of the bed by pillows to 30 degrees, and avoiding lying down for least 2 hours after food.
If these tips do not help, then liver function test, pancreatic enzymes, and HIDA scan for gall bladder should be done. Food intolerance and inflammatory bowel conditions such as IBS, Crohn’s, etc should be considered (celiac is ruled out in your case). Log in what you eat and see if there is a correlation between a certain food type and the symptoms.
The weakness in right arm that comes after food can be a vaso-vagal attack. It can also be a nerve pinched in the neck due to a bad reflux.
I sincerely hope you will find this information useful in your journey towards better health.
Hope you get well soon! Good Luck and take care!
Sounds very similar to what my husband had experienced, abdominal pain, gas, bloat but no nausea, are you on any NSAIDs, or painkillers? Some can irritate the stomach, in his case he did have h pylori gastritis though, which has supposedly been eradicated, just waiting on biopsy results now due this week, I have always said you only have one body so always err on the side of caution, if your symptoms are not normal for you always get it checked