Autoimmune won't show celiac. Scratch tests may or may not pick up wheat allergy, depends on the type.
Maybe you could at least get the blood test for celiac before rushing about
changing your entire life going gluten free.
If you haven't had GI problems like D all your life, I'd bet on an allergy or intolerance first. New allergies and intolerances often show up in adults, even seniors. Celiac shows up in little kids if you know what to look for. After a pasta meal you can end up in the ER. The D makes people lose huge amounts of fluid.
I'd take one thing out of the diet at a time, logging it in the food diary. Try it for a week. I'd start with lactose before wheat. It's easier. You should be able to tell within a couple of days. Keep on with the lactose-free milk, but no cheese, regular milk, ice cream, yogurt, cream, creamer.
And hold the magnesium.
Bile salts are made from cholesterol by the liver to aid in digestion of fats.