this will go against the grain (sort of) for some but...my dog is 4 weeks preg 9lb expecting 5 pups she is 2 years old and i could tell from 2 weeks....
the milk bar gets a little bigger. right now she sleeps loads and is slightly off her food.
2lb is a bit small so perhaps be ready for c section if she is past 28 days then a vet can scan. right now at 32 days i can feel pups when i put my fingers lightly on her belly.
i couldnt upload a photo but this should giive you an idea...it is my facebook photo album
puppies | Facebook