Best thing you can do if u decide to breed again is get your vet to do the pre-mate test on your bitch, It tells you when the female is ovalating, Once the vets give you the go ahead you can use your stud on her or rush her of to a lined up stud..if nothing happens if you use your stud then maybe it is your stud thats the problem?.
Also i had a m8 of mine whos female carried only 1 pup, It was a day late so she ended up having a c section and it survived
, I've heard that pups being born stimulate eachother and if there is only one pup the chances of that being born all by itself are slim because they need the stimulation of the others to help it on its way.