If you're not sure why don't you visit the doctor and get tested for Celiac disease? It's quite a common condition. More than 2 million people in the U.S. have this disease (if not more), so doctor's are well versed in administering the test for it. It's just a blood test, followed by an intestinal biopsy if the blood test turns up something.
I'd imagine doctors would be more willing to test for Celiac disease anyway vs. Candida. At least then you could narrow down your search a bit more.