Go gluten free for a while. Your symptoms *could* be Celiac disease, or just gluten intolerance. Gluten intolerance doesn't mean there is something wrong with you or that you are "sensitive" to gluten, it means that your body is smart and telling you that you shouldn't be eating gluten. And... no one should be eating gluten in my opinion.
Also try a dairy free diet. You could be lactose intolerant, or maybe just rejecting dairy because you are not a baby and especially not a baby cow. Eat adult food instead of milk - you are past the age of weaning off breast milk. An *adult* digestive tract is not designed to digest milk or dairy. You can survive on milk but you will not thrive on it.
The body protects itself against milk and gluten by for example... forming a mucous layer on the intestinal walls or inflaming the intestines with antibodies, both which cause bad digestion and lack of nutrient absorbtion.
Just because you are not diabetic does not mean that you can't have blood sugar / insulin problems. Doctors and lab tests have their place but they are usually useless for diagnosing. Congratulations for taking your health into your own hands.