That is really unfortunate, a young dog should not leave his mother at that age as he loses many of the socialization experiences he needs. When he tries to nurse with his sharp teeth, he hurts her, she bites him, and he thus loses bite inhibition. This is something you are going to need to teach him. (Look up articles on bite inhibition training.) A lot of puppies here are sold at one month, and do okay as long as they are adequately socialized with other dogs at their new homes. If not, they become dog aggressive or fearful. Do you have another dog?
As far as your question goes, Nettlemere is correct in recommending you take te puppy in for a physical exam and to check for worms. It may just be related to the stress, but you should not take that chance. The vet tech will also recommend a puppy food available where you live, and answer any other questions you might have. Make a list of your questions before leaving home so you do not forget once at the vet´s office. Good luck with your new puppy.