Keeping in mind that I don’t have a medical background, I have a low opinion of diagnosing celiac with endoscopy. The biggest problem is false negatives, depending on where the biopsy is taken and the severity and location of celiac-induced damage. In your case, there is the confusion with possible giardia damage.

Further testing might be helpful. You mentioned starting a gluten-free diet: has this helped? It may take weeks or longer before you notice a difference, and if you cheat, you have to restart the clock but if you can stick to it for a couple of months and if you feel better, that too is a strong indication. Given your long history of celiac-like symptoms (sounds familiar!) you should know if you consistently feel better than before your giardia encounter.

No, mold does not cause celiac disease.

Celiac disease is a genetic condition triggered by gluten.

Some people do not experience symptoms until later in life, and it could be that mold exposure or other stresses on the immune system could push someone with celiac disease over the edge as far as manifesting symptoms.

Even if this is not the case, many types of mold are toxic.