The gold standard test for celiacs disease is a endoscopy. They take a biopsy of the small intestine and look for damaged villi. Blood work can have false positive results - an endoscopy can't. In order to have a endoscopy test for celiacs you need to be eating gluten because if you don't then you can invalidate the test.
If you are still worried about gluten then ask your GI for a endoscopy.
-------------------- STABLE: ♂, IBS-D 50+ years - Science of IBS