Weird symptom?

I've always had a sweet tooth and pregnancy hasn't changed that. However, when I have sugar (candy, juice, even some fruits!), I get such a yucky feeling. I usually get a headache and lightheaded/dizzy and have to lie down. My stomach just feels gross too, like if I had overdone it on Halloween or something. Has anyone else felt this way? I'm nervous it could be gestational diabetes or something but it seems too early for that to be showing up.