To my understanding, any digestion related problems (gluten and lactose especially) occur when there are certain proteins that require enzymes to break them down.
So, basically the struggle we have to break these down is actually not an allergy, but a lacking of certain enzymes that can handle the digestion of such proteins.
I also tested negative for Celiac, but I have a sensitivity to gluten. And, I am completely lactose intolerant.
I have been tested for allergies and coeliac disease but they have all came back negative. So I only have an intolerance to wheat