Hi, as Sarah said, please don't let yourself get anxious it won't help you or baby.
I had my baby at 38+3 but I have read many ladies on here getting induced after that, I think 38w seems to be the average but lots have done it at 39 & 40.
I assume your diabetes team and consultant have been closely monitoring you? If they did not think it was safe for their plan to happen they would change it, however if you are really unhappy with it have you tried speaking to them about this? Don't do something you really don't want to do if it is going to make you more anxious.
I also worried about going into labour and not knowing, didn't happen for me though.
Good luck, let us know how you get on xx