I'm afraid that I don't have any real words of encouragement or comfort but I do have an idea that may, depending on your situation, may be helpful.
After a lifelong tussle with my stomach/guts, I was diagnosed with IBS. I was lucky enough to get the combination type; some C, some D. The positive behind that diagnosis is that at least I know what's causing my disomfort. Knowledge, as they say, is power.
I assume you are following a low FODMAP diet. That has worked well for me.
In all your diagnostic work, have you been identified as having GERD, and, if so, are you taking a PPI to control it? I ask because some PPI drugs can cause terrific intestinal cramping and diarrhea of biblical proportions. The first one I took left me with a case of potty-lock for about 4 weeks until I called my gastro. He changed my PPI to a different formulation (apparently there are several), and this one works as it should.
I discussed my situation with my general physician. We discussed the potential benefits of hemp products, specifically canabidiol (CBD) in the treatment of IBS and other gastric difficulties. I started taking a CBD infused honey - I know it's not low FODMAP but the quantity I use has no negative impact on my system. I use about 15 mg/day and that seems to be the right dose.
Because hemp and CBD are reasonably new in the world of treatment of IBS, I have done a considerable amount of research on the subject (based on scholarly articles in medical and biological research journals) and am convinced that it does have a place in my course of treatment. You may want to discuss this with your doctor.
I wish you every good luck as you find a course of actions that leave you well and happy.