@beanie300 What I don't see in your tests anywhere is gluten intolerance or Celiac disease. You describe a lot of GI type pain, joint pain, skin rashes, brain fog, numbness/tingling, mouth ulcers, nausea, diarrea... that collection could be a gluten problem. Your description gives so much detail and shows how much work you've done to try to figure this out. A lot of doctors only look at things inside their own specialty, so maybe they are missing this. You can test yourself for this if you stop eating all foods containing gluten. You need to study to do that as there are many hidden glutens in processed foods. If you eat plain meat and veggies for a few days with no spices or sauces, and no products made from grains (except rice or corn which are gluten free), you can see if you feel better. I can't eat gluten or I get very ill. I took gluten out of my diet 20 years ago when no doctor would test me for it and a lot of doctors didn't believe it was a real problem and my symptoms cleared up immediately. Also know that just because there are gluten free junk food products now, that doesn't make them healthy. Sugars and processed carbs are just that and can promote diabetes with or without gluten. You may know in just a couple days if you eliminate this from your diet. That could be part of what could be wrong, and it would be a start. Sometimes it can be a number of things to discover in steps to get back to health again, and if you get one problem out of the way, the others may be easier to deal with.

Here is a link to the Celiac Disease Foundation about the symptoms. https://celiac.org/about-celiac-disease/symptoms-of-celiac-disease/ and Mayo's link about Celiac disease https://www.mayoclinic.org/diseases-conditions/celiac-disease/symptoms-causes/syc-20352220

I know that the large intestine passes on the left side on it's way to the rectum, and if that's inflamed, you could feel pain there. Celiac disease is an inflammatory condition where the body attacks the GI tracts because of gluten (sort of)... it's actually the protein gliaten which is attached to the gluten that causes the trouble when they named this, but at first they thought it was gluten. These are found in almost all grains. Humans did not evolve to eat grains, but at the time we cultivated grains as a food supply, it allowed our species to proliferate. There is a good book about all this called "Going Against the Grain". Reading that changed my life.