WHY do you want a litter? Are your dog and bitch prime examples of the breed? Are they both from well-bred and eye-tested stock and purchased from reputable breeders? Have you enlisted the advice and help of the breeders of either dog? Are they kc registered?
It's not recommended to breed from a sire who has not been eye-tested and who is only a puppy himself. The best thing you can do is seperate the dogs, and if no pregnancy has occured, wait until the next season.
In the meantime, perhaps you could prepare better for the mating, pregnancy and whelping? And decide why you want to breed?
Rescues are overflowing with dogs needing homes, so it makes sense that we are all responsible, and that people only breed for the right reasons...to improve their chosen breed and to produce happy, healthy, temperamentally sound puppies who they will remain responsible for long after they are homed.
If your bitch is now pregnant, then I hope you will read the book of the bitch and be as responsible as possible with the pregnancy and puppies. I'm sure you will find people here will give you advice regarding any minor problems you may encounter.