I had all the same symptoms as you. Still do at 32 weeks. I had an 11 lb baby my 1st time and I was sure that they just "didn't catch" the diabetes.
So this time I was sure I would fail my test. I passed with flying colors, not even close to having GD.
You really need to keep up on your eating and make sure that you're not taking in too much sugar. That's my problem. Drives my husband nuts when I've been busy and haven't eaten in a while, then BAM!! I'm suddenly going to pass out or vomit unless I get food in me NOW! Or if I've only had something sweet to eat in the past few hours, same thing.
Mention it to your doctor. I don't know if they test earlier. Maybe they don't see it to be a problem until you're further along. I'm sorry that you feel yucky