You sound like I did before I was diagnosed with a food intolerance. it could be intolerance, allergy, or ulcer maybe?
Go here to learn about gluten intolerance:
the list goes on. Please keep a food and symptom diary, record everything you put in your mouth including medicines, vitamins, gum, etc. as well as how you feel, and what your symptoms are. This will help your doc determine if it is a food allergy/intolerance. Good luck!
Perhaps, gastroparesis or gastritis:
If, gastroparesis, prokinetics are very helpful. Domperidone is a good choice. 10 mg tds. It doesn't cross the blood-brain barrier (penetrates it less, actually), so risk of side effects is less when compared with metoclopramide.
If, gastritis, make sure your doctor screens you for h. pylori (preferably, a c-urea breathe test). This organism is often the culprit in gastritis. Prevacid (or any other PPI) is a good choice. 30 mg bid, probably best, initially. You can always titre down. H2 antagonists are subject to tolerance, so probably not a long-term solution to your chronic symptoms.
Histopathological analysis of biopsy from esophagoendoscopy is the gold standard for diagnosing gastritis. Gastric emptying studies are best to assess gastroparesis.
BTW: I hope you get the help that you need. If you are inclined, please share it, after you've attended the medical appointment.
In general, I find doctors are typically good at diagnosing things that fit nicely into a box, but not so good at diagnosing chronic as well as complex issues.
Hope your issue is very simple, treatable, and you will look forward to wellness very soon :-). Sounds like you've been suffering with these symptoms for some time, already :-(.