My friend could have written everything you said. He had narrowed down to a very limited diet and lost a lot of weight because almost everything he ate either c

My friend could have written everything you said. He had narrowed down to a very limited diet and lost a lot of weight because almost everything he ate either came back up or rushed right through him. He hadn't mentioned neurological issues, but he did switch to working at home full time to isolate himself, so that might have been a factor as well. I'd strongly recommend trying FMT. Whatever downsides and risks there are, can't be any worse than what you're going through.