NST and AFI Testing

My scheduled c-section date is September 27th and this week I am starting NST and AFI testing 2x's a week. Is anyone else doing this testing yet? I didn't do any of this testing with my first baby and this pregnancy is no different. I have gestational diabetes which is being controlled by diet which I did for the first baby too. What can I expect during this testing? And is there a chance they'll move my due date up? I'm only 33 weeks.