
As I've said before, with mine I didn't let them go over the due date, counting from the first mating (even if conception doesn't take place immediately) by more than 2 days. There is a point at which those puppies need to come out. So at the very least I'd be seeing my vet today - after all they keep growing making a natural whelping less likely to be possible and a C.Section more likely to be needed.
With small litters (numbers) they can just sit - and grow.
I've known vets not be worried (not my own because if I suggest it's to go in, they usually do!!) - and half the litter or more, be lost!!! And btw, it's when the temperature goes down, and stays down, that usually means whelping should start within 48 hours. Not that I set much score by the temperature readings but if it flucturates, up and down, whelping won't be about to begin.