I have never had a sweet tooth and when i rarely do eat anything relatively sweet (fruit/deserts) i get very weak, faint, and nauseous, why?

A glucose tolerance: test will tell you how your body metabolizes sugar. It is much more helpful than a simple fasting glucose test which measures one point in time. Your doc may order this if you mention it. Peace and good health.

Carbohydrates: Some people have a metabolic disorder that causes this problem. Usually involving carbohydrate metabolism. I would ask your physician about this. Did you notice this problem when you were a child? Ask your physician and see if they can get a diagnosis for you. I sucks not being able to eat any sweets. I guess on the other hand you probably are consuming less calories by not having a sweet tooth