Glucose test.

I didn't pass my one hour so I had to do the three hour and I didn t pass that one either. So I had an appointment with the dietician. I've had to check my blood sugar your times a day she told me it should be between 70-120 every time. I've been staying in the 80s besides a 45 and then a 21. What can happen when my blood sugar gets that low? I called the doctor and he told me to eat right away. I've been doing everything they told me to do so I'm not sure why it was that low. I have an appointment on Wednesday but was wanting to see if this has happened to anyone else? will they make me stop the diet or what.