A single investigation which is likely to most helpful in diagnosis and cost effective for your symptoms would be CT scan of abdomen. Following would be the consideration of the diagnosis;
1) Gastroparesis; slow emptying stomach
2) Hiatal hernia
3) Intestinal obstruction chronic (due to adhesions)
4) Irritable bowel syndrome
Following may help you, meanwhile you are investigated;
2) This may help;
a) Bismuth subsalicylate
b) Activated charcoal
c) Simethicone; (Maalox, Mylanta); Simethicone causes gas bubbles to break up.
d) Beano; contains an enzyme (alpha-galactosidase), which helps to breakdown certain complex carbohydrates.
All are available without prescription.
Avoid foods that appear to aggravate symptoms. These may include milk and dairy products, certain fruits or vegetables, whole grains, artificial sweeteners etc. But this is based on the personal observation for the aggravating food.
Discontinue the following if you do them;
1) gum chewing,
3) drinking carbonated beverages, and
4) gulping food and liquids.
Please feel free for your follow up questions.