
This happened to a good freind of a freind of mine. She decided to offer an unwanted bitch a home, chose a GSD cross bitch of about 10 months, who had been there several months, but she had to wait until her season was over.
After she had her home some weeks she was getting pot bellied, and despite plenty of food wans't getting much meat on her bones.
When she took her to the Vet she was horrified to find she was in whel, so obviously this had happened at the Dogs home.
They decided that the best thig to do was to let the bitch whelp her litter, and leave her two pups to assuage the maternal instinct, and have the rest of the pups put to sleep, (she had 9 all sorts of colours and patterns). The bitch was really only a pup herself, and they felt that they could find good homes with family and freinds for two pups, but couldn't guarantee the future for the others.
Your bitch is of a big powerful breed, and it is impossible to know what she was mated with. The combination of breed traits may be unfortunate, or even dangerous. Say the sharp reactiveness of a terrier, coupled with the strength and power of a Bully????
I would urge you do as my freinds friend did, and only allow her to rear two pups which you home with the utmost care, and have the rest put to sleep straight away.