If this is a new behavior occurring after giving birth, it may be a good idea to visit the vet to make sure everything is OK. The frequency of pooping and the amount of accidents you describe sounds like something must be going on. Perhaps she has a bout of colitis or perhaps she doesn't want to leave the puppies alone and she's mildly stressed. Many mother dogs ingest the puppy's placentas and this can cause their stools to be soft and trigger some accidents. If that's the case the pooping should subside, but certainly, see the vet make sure there's nothing else going on.