Blood tests negative, but gut acts positive for gluten intolerance?

Avoid it.: Not sure what testing you had done, but... If you reliably develop symptoms with ingestion, then stop eating it. There are two common wheat related issues - one is gluten enteropathy ( celiac sprue) which is a destruction of the lining of your small bowel and the other is wheat and grain allergy. They are different diseases and require different testing.

Gut acts positive ??: There are a many conditions with overlapping symptoms effecting the gut. You don't list why the gut acts positive, which limits my answer.You can have intolerances to a variety of foods, artificial food dyes (red #40), and others, that will give symptoms but not trigger the immune tests for celiac disease. Keeping a food diary & eliminating/re-adding potential agents is one way track them down.