what is celiac disease? what is the diet to go with it? how does it work with gerd and diabetes and diverticul

i also have migraines and fibromyalgia and kidney disease and ibd. the last word is suppose to be diverticulitis in the question. i need to lose weight and am having a hard time getting these diets to work together and i'm just getting bigger and bigger even though i still exercise. i also suffer from a tilted pelvis and spinal stenosis and radicuopothy.