My daughter had a single weak positive blood test and there was visible damage observed when she had the endoscopy. Biopsies confirmed celiac disease. The blood results are not always a direct reflection of the degree of damage.
The frustrating thing is that the blood levels don’t actually give you an accurate picture of the internal damage that is present. My daughter’s TTG levels were considered mildly positive, yet her GI could see celiac related damage with her naked eye during the endoscopy. I would fight for thorough follow up, whether it is with this doctor or another one...