Does anyone know what normal blood sugar levels are during pregnancy?

I've been testing my blood sugar because there was a concern for gestational diabetes from a previous metabolic disorder. However I've noticed that my numbers seem low. Like fasting it's been 65-75 and 2 hours after eating it's been in the 70s. I feel weak and I've been losing weight even though I'm eating loads of carbs/junk food and doing nothing all day. Should I be worried?