Generally, you can tell if your dog is pregnant by feeling the base of her nipples. Squeeze them gently at the base, and if they feel swollen or if it feels kind of like a round squishy thing... then that is the milk forming in her nipples and she is most likely pregnant.
Well did she all of a sudden start gettin bigger? Put ur hand on her tummy and c if its hard or if u can feel puppies moveing around
If she is pregnant then she should go to a vet and get checked, he can also help you diliver the pups when she starts whelping