I had the same symptoms after meals during my last pregnancy, but much later (maybe from 28 weeks on). I asked my midwife about it and she said she hadn't heard of that. I personally believe that for me, it was a symptom of uncontrolled GD -- I passed the 3 hour GTT with one abnormal reading, but I ate a TON of sugar (drank chocolate milk every day, had a large dessert after dinner every night, etc.) all the way through the pregnancy and think that my blood sugar was probably spiking pretty high after meals and that this caused the racing heart.
That said, I also think that GD is often preventable by changing diet and exercise habits -- and that it's overdiagnosed and invites unnecessary interventions like induction. I would suggest smaller meals, cutting out all refined carbs, and exercising daily. I've been doing that since 24 weeks with this pregnancy and I have felt so much better (though I hate having eat like I'm on Atkins). I am pretty strict about the carbs -- no bread except low carb toast at breakfast, no pasta at all, a little brown rice maybe from time to time -- and make sure to balance any carbs you eat with protein and fat (including fruit and milk, which has lots of carbs). I eat a LOT of string cheese and salad.
Given that you're only 8 weeks, is it possible that you were diabetic or pre-diabetic before the pregnancy and were unaware of it? It might be a good idea to test your fasting glucose or have that done at your care provider's office to see where you are.
Or, the dizziness and racing heart could be something else entirely for you. I hope that it is not anything serious. Good luck with the rest of your pregnancy!