Gestational diabetes...advice

So I was diagnosed with gd on Wednesday after failing my 1hr glucose tolerance test. I'm currently 16w2d. I can't get in to see the dietitian until the 24th, but was told to watch my diet and monitor my blood sugar 4x a day (upon waking, and 2hrs after each main meal of the day). 
Any suggestions on how to cook for this new lifestyle/condition and what not to have? I've been told count calories and I have also been told to count carbs not calories. 
I should also mention that my OB thinks I might have had undiagnoised diabetes before getting pregnant since I was on Metformin for over 2yrs due to pcos