from what i have learned from all the breeders, one can't tell how long into the prego they are, you also need to remove the male when she has the kits cuz he can breed her again, and that really isnt the best thing for her.
and please be careful with breeding, no matter how much researcch you did on the web, trust me you are not ready to breed, i'm am not saying that to be rude, i am saying that cuz i was asking breeders lots and lots of questions at one time and thought i was ready, and i found out, i wasn't. you can't believe the things that couldd possibly go wrong with chin prego. i'm not saying it WILL happen, but can happen and you can end up with a very broken heart. i have heard stories that are so scary.
i do hope everything goes smoothly for you.
ps one way to tell if she is close to delivery is if her teets are very long and the ends are white..pregnancy's last 111 days.