Coeliac Disease -- otherwise spelt Celiac -- is a sensitivity to a protein in grains known as Gluten. The condition also glories under the name of gluten sensitive enteropathy [intestinal damage]. It is genetic but doesn't necessarily develop from birth; it can be triggered later in life by another condition or disorder. Coeliac Disease affects about one in a thousand people in Britain, though it's more prevalent in Ireland. It is incurable and can be dangerous if left undiagnosed but a gluten-free diet will keep it under control.
When a Coeliac eats or drinks anything containing gluten, the body can't digest it and the immune system kicks in. This damages the villi -- tiny finger-like do-dads that actually digest the food in the small intestine -- which affects the absorption of nutrients.
Once you've been diagnosed (based on your symptoms and on tests), the only answer is to cut out gluten. There is no other treatment and no cure. Living gluten-free isn't too difficult at home; it just requires some thought and a bit (or maybe a lot) of sacrifice. Shopping can become a grind but you quickly get a feel for what you can and can't eat.
Gluten-free outside of your own home is a bit trickier. Family and friends can be horrified and/or completely clueless [though not my own family, obviously!]. Restaurants and cafes often aren't geared up to deal with someone who sounds like a whinning whatsit. The less of a clue they seem to have, the more specific you need to be and the more annoyed they get. This isn't always the case, though; many places are happy to help out and deal with your requirements in a pleasant and understanding way. That's great but it doesn't entirely make up for the times when it feels like a trial by fire.
That said, once you get in to the swing of things it really isn't so bad. Give yourself time to mourn the things you love but have lost. Take some bumph for your folks to read. You could even point them in the direction of this site. Phone ahead if you're going out and make sure they know that Coeliac isn't a small formerly-Soviet country. Get baking if you're a cake-aholic like me; there are some great gluten-free cake mixes around or (better still) bake your own gluten-free treats.
In short, accept that you have to live this way because you're in it for life.