A little concerned

I was told that by my doctor that I have gestational diabetes. I have been following their meal plan to a T. Exactly doing what they've told me to do and even doing the exercising they've told me to do. I'm very confused as to why my blood sugar is consistently testing very low, as in low 50's to low 60's. My normal blood sugar before doing this diet was between 70 and 80 all the time. Should I maybe go back to what I was doing and just keep the exercise? I have always followed a diabetic diet plan before this, but the doctor changed my meal plan around and now I'm always feeling hungry and shaky. He upped my calories by 300 a day, but I'm not feeling like I'm eating right...I keep telling myself that the doctor knows best, but I'm beginning to think he really doesn't. I have an appointment on Tuesday to see how my testing is going and I'm worried that they're going to think I'm starving myself or something. I always keep a food diary, so I plan to go in armed with that as well.