Sounds like maybe FODMAP trouble, but I suspect your main problem is that you don't eat anything. And what little bites you do take are often fibrous. I am a burp and fart storm if I eat something bad to me, like some cookies or too much fruit.
Have you tried just 0 fiber to see how you feel? Liver, steak, fish, eggs, cheese, drinking fats like coconut milk, tallow with bone broth in it, etc. for a few days? I do that often, and feel amazing!
Steak, eggs, potatoes - fruits, nuts, berries and forage. Coconut milk and potent herbs and spices. Tea instead of coffee now and teeny amounts of kelp daily. Let's see how this does! Not really had dairy much, and gut seems better for it.