You mention having all kinds of tests done, but specifically was an MRI or CT of your abdomen done? How about a colonoscopy? If those have been done and are negative for pathology, I'd say get another MD second opinion. Good luck!
Being a nurse I don't have all the answers. I think maybe if I were you I would possibly see aw different GPractitioner. I know you said you've had the workup but to me something is missing. So, you had a colonoscopy and endoscopy? They did a scope and took a small biopsy of your stomach and was all negative? Did your gastroenterologist suggest medications. What I would be very concerned about is the weight loss…Thats a lot for just a few months without trying. I think you need to get another opinion. I know this also depends on your insurance and I hope you are able to do this without a problem. I wish you a lot of luck and I hope they find out what your underlying problem is. Be well Take Care
Make sure you get some basic nutrition in your body, despite the fact that your taste and appetite are very low, because you will soon suffer severe consequences of malnutrition with possibly irreversible damage.
Products like Ensure or Boost will supply you with the basics, for the time being, until you get this sorted out.
Have you ruled out Celiac's, gluten sensitivity -Look into Gliadin test (urine), by Cyrex labs. They test 12 forms-not just the alpha ordered by most doctors- of gliadins regarding gluten intolerance (not necessarily just digestive)- Candida, Leaky Gut Syndrome?
Some of these are missed because they are not recognized by conventional medicine, or the proper tests are not done.
Let me know if you need more details.
Wishing you well.