There are three levels to gluten sensitivity. Gluten is found in Wheat, Barley, Rye and can be found in oats because of contamination in transport or growing fields with gluten grains.
-Sensitivity, where you have some irritable symptom from ingesting gluten, but doesn't cause any long term damage
-Intolerant, symptoms are more severe and can last for several days...could even be migraines, like after drinking beer
-Celiac disease, can be the hardest to diagnose because the symptoms are so different in different people. And some have no symptoms at all, which is worse, because to continue eating gluten with celiac disease increases your chances of colin cancer by 30 times! It destroys your villi in your small intestine, therefore you receive no nutrients from any of the good food you eat. Common symptoms are bloating and loose stools or constipation, thinning hair, premature graying hair...the list is long, again making it so hard to diagnose.
It takes about 6 weeks for your intestine to heal, so Celiacs don't fall of the wagon intentionally. There is a blood test you can take but it can give you a false negative, but not a false positive, otherwise the only 100% true results is from a scraping of the villi...and it is important to have been ingesting gluten prior to get an accurate test.
Personally, I don't recommend eliminating gluten, if you don't have to, if you are just going to replace it with all the gluten free substitutes on the market. While I appreciate the cookies, muffins, cakes, breads as much as anyone, they are typically twice as high in fat and sugar with little to no fiber. So it's important to limit the substitutes and stay as natural as possible.
I was diagnosed 5 years ago and it turned my world upside down as I LOVED baking. Yes, there are alternatives, but again nothing quite as good, with quite enough fiber, and much more expensive to make.