Oh my gosh, I am SO SORRY you are suffering like this. I know how horrible gut troubles can be! I get gas, bloating, belching, gut gurgles, upsets & nausea more often than I'd like. [ONCE is too often!] Every time I eat, I worry how it'll affect my tummy & gut!
I take grape digestive bitters, esp. with meat meals; and also sip hot tea with a slice of ginger OR a splash of apple cider vinegar to help digestion. But your symptoms appear to be way beyond these simple therapies.
I also eat probiotic foods ... not milk kefir ... although I do give that to my cats for health ... but homemade sauerkraut, pickle relish & apple/cranberry/orange relish. Actually I read somewhere that pickle juice helps digestive issues. I would guess my sauerkraut juice would do the same. Takes about two-three days to ferment, then you can dive into it. Just a thought. If there IS a bug of some sort causing these problems, I've read Iodine can help, too.
Obviously something has triggered and really upset your digestion and I wish I could suggest more to help you, something to calm it down and heal it so it functions as it's suppose to. Have to checked out earthclinic.com? My view of docs is the same as yours. Glorified pill pushers.
I hope someone else will chime in with some advice soon. In the meantime, maybe just switching to water, herbal teas & homemade and/or natural broths for a time might help some?