If you can bear it yourself, I would actually take the trouble to confirm. The reason I say this is that you will be at higher risk for iron-deficiency anemia, osteoporosis, cancers, neurological problems, and other autoimmune diseases. The risk goes down after removing gluten for some of these complications, but not all. I don't mean to be all doom and gloom - my point is that it's usually good to know if you're dealing with celiac because then you and your doctors will be more aware should you develop symptoms of something else that benefits from treatment - especially when there is a better prognosis depending on how early it's detected.

On a lighter note, the people I have met who have celiac say that cutting gluten from their diets was a game changer in terms of how they felt. They just felt drastically better once they knew and had instituted the correct diet. They didn't even realize how bad they'd felt until they could look back. So if it is celiac disease, you can look forward to feeling much better.

P.S. I'm not so sure that the endoscopy is to confirm celiac so much as it's to rule out other causes as well as to determine the extent of intestinal damage, but I could be wrong. Although many people with celiac have intestinal changes specific to the disease, not everybody does.