“How accurate is a celiac blood test?”

Blood test for celiac disease is 98% accurate on patients with celiac disease who are on gluten contains diet.

Celiac panel is fairly accurate but gold standard to diagnose celiac is small bowel biopsies during endoscopy

What test did you doctor order? It may not be accurate in early stages of the disease.

It is quite accurate, but you need to be on a gluten containing diet before you check it. Also, a small proportion of people may have what is called IgA deficiency and in these people the celiac antibody test might be negative even if they have celiac.
For those with a positive celiac antibody, the next step is endoscopy with biopsy to help confirm the diagnosis. A good GI doctor should be able to confirm or rule it out.

https://celiac.org/about-celiac-disease/screening-and-diagnosis/screening/