I think it's a combination of antibiotics, mercury fillings, environmental toxins/triggers, and genetics that messes one person up but not another.
You could try taking HCL and digestive enzymes with meals (but don't take HCL without protein). L-glutamine and slippery elm are good for repairing the intestinal lining. Colostrum is also supposed to be beneficial but I think you'll have to find a good source to see any effect. One person on here got rid of the candida overgrowth by drinking a gallon of fresh colostrum. You'll probably have to get good quality from a farmer to cure candida/bacterial overgrowth; the colostrum in capsule form doesn't seem to be doing anything for me.