A couple years ago I was very sick. Vomitting, diarhea, nausea which lasted for about
8 weeks. I had every test known on almost every body part and everything was fine. I finally ended up at a gastro dr. He did a colonoscopy which showed inflammation but nothing else. He told me to eat plain noodles (at the time I didn't know I had celiac, so I was eating regular noodles) He said that it is the easiest thing for you to digest and it is full of carbohydrates so it will help you gain weight.
Since you have to do gluten free, I would suggest getting some white rice noodles (they would not have as much fiber as brown rice noodles) and eating them. You could maybe also try white rice, and plain baked potatoes. It doesn't sound very appetizing especially after you've eaten it for several days, but it will help calm your stomach down enough that you could then start adding things back into your diet.
I hope this helps you, I can certainly sympathize with the constant nausea and stomachache. It isn't any fun. I hope you get feeling better soon.