depression after having puppies

hi, i recently acquired a pitt she was dropped off and fell in love with my husband so we adopted her. well she was pregnant and 4 days ago had 6 puppies, now she seems depressed and sad all the time, is this normal, should i take her to the vet? (she went to the vet 2 days ago before i noticed this for after birth check up) i have never had dogs before so any advice will be greatly appreciated