advice

without sounding too rude, if you had to read on the net how long your dog should be pregnant for I dont think you do love your dog that much.You musn't have done that much research. Did you even think about the cost involved in having puppies, or the risks involved with your female? Do you know how many unwanted dogs and cats get killed every single day. We really do not need any more unwanted puppies in this world

A call to your vet will answer the questions you have on gestation.  You can also go to the websites on your particular breed especially for what dog clubs or associations you belong to.  Keep the information with all her important papers including her pedigrees, conformation results, testing, and xrays you may have done before you bred her.  From your post I can't tell what her breed is, but you must be excited at the prospect of puppies taking over your home in the near future.  Hopefully you have had an attorney draw up a contract for your buyers to sign protecting yourself in the event you need to re-home any pups, and allowing you to check on the homes of buyers to make sure they are appropriate families, and making the buyers promise under no circumstances will they breed their new dog.  (Spay/Neuter Clauses) Hopefully her delivery is uncomplicated and all pups are healthy.  Best of luck, Jules

what a way to break my heart, so early in this morning....
I'm saddened that you have chosen to allow your pup to breed.  And it seems like she perhaps hasn't seen a vet for a while, or you might have the answers to these simple questions a vet would be able to let you in on....
It might not be the answer you're looking for, but what I have to say is, PLEASE spay your "beloved" dog as soon as you can after she delivers. 
If you'd like low-cost options for your area, I'd be happy to get that information to you...
What you're doing to her highly increases your dog's chances of developing many different kinds of cancer, which will cut her life short and cause unimaginable pain and suffering toward her end....
If you love your dog as much as you proclaim, please do something to protect her and others like her, and stop being irresponsible and allowing her to breed.
Please do NOT offer the puppies out as "free to good home".... take the responsibility of what you have produced and ensure they go to quality homes....
you have NO idea how many impulse grab puppies who were picked up "free to good home" who, once they outgrow that adorable little baby-puppy age, get abandoned, abused, and dropped off at shelters to meet a lonely, desolate future and a trip to a steel table to be killed because they're now older, and unwanted, and unadoptable.
Out of sight should NOT be out of mind for you, as a pet-lover.  You should value your dog's offspring as much as you do her... the best way would have been to prevent the whole thing to start with, but too late for that, so PLEASE be responsible in placing the pups, and PLEASE, then, spay your dog. 
thank you   ~ Julia

this is really a heated topic (as i personally know) its really a complicated topic and quite difficult being a 1st post. BUT whats done is done and all I can recommend is taking this girl to the  vet ASAP. God forbid she is having problems with the pups.
 
Im sorry if I sound harsh, but if you really love your girl you should have taken her to the vet from the moment you thought about breeding her.

OK folks, this wasn't a real bright thing to do and I'm gonna guess that no genetic testing was done since the OP doesn't even know the length of a pregnancy. But what's done is done and swiping at the OP doesn't help the DOG, and the dog is why we're here. 
 
NO dogs do NOT carry 75 days.  She is now 3 full days past her due date and needs to be vetted.  Has her temp dropped?  You HAVE been checking it, right?  I had a cocker I would have lost if I hadn't gotten her to the vet following my GUT that something was wrong....her and the two enormous pups she was carrying.  This is NOT like people that they CAN go past their due date (although docs shouldn't allow THAT either).  You KNOW the date she was breed, and she is PAST due now.  Please get her to the vet immediately.

Please take your girl to the vets .
 
Sometimes I wonder if people post stuff like this just to get a kick out of the responses that they get. Especially when they post an after recieving any response they never seem to have anything to say afterwards.....Just a thought? Not really saying it will be that way with this post seeing the OP did just post early this am an may very well be back to respond. Really just thinking in general.[8D]

I think sometimes, with some posters, they just don't like the answers they get.  Again, only talking in general terms.
 
Please take your dog to the vet - if she does come through this OK, please have her spayed.
 
Kate