Go to the vet RIGHT NOW!!! You pup may have parvovirus, which is fatal in untreated cases!
Gabby, you have an Emergency on your hands! This little one should still be with her mom and still nursing.......You must get her to a Vet ASAP......She will go downhill very quickly......It would be best to take her to an Emergency Clinic, now.......Please, do not wait......She needs help.....I hope everything works out for her......Bless her heart! Karla