Your rabbit may not of mated on that day. I thought my rabbit had mated but it was a couple of days later as the birth was overdue, as I thought. You do really need to take them to a vet to be sure they are actually pregnant.
Has the doe that is due made a nest? although not every doe makes a nest well before they have them, my doe made a nest the same day!
I would really reconsider your thoughts about breeding as really there are no "up's" just "downs"
My rabbits first lot of kits all died, all 6 of them, then another 3 in the next litter died too, very upsetting.
I now have baby rabbits which whom Im trying to home, with no luck so far. Although I am making sure they go to good homes maybe this is why.
And another big down is going to be seeing them go. I have seen these little babies grow from day one and really fell in love with their little personalities, its heartbreaking to think I will never see them again.
Although they are very cute most people buy them for the wrong reasons, for their kids or whatever, and they just end up sitting in a hutch not getting bothered with, and one day will be passed to another home.
There are millions of animals unwanted in this world please have a good think about that before adding to the problems.