What else besides diabetes or hyperglycemia would make you become nauseated after eating sweets?

After experiencing gestational diabetes with my last child, I have to be very careful with sweets. That was over 25 years ago, but ever since then, if I eat anything sugary on an empty stomach, or if I have that second piece of cake, I feel just like I have a case of “morning sickness” – nauseated and basically grossed-out. I have had myself tested for diabetes and hypoglycemia and the tests have come back normal. So why do I feel like this?