Oh boy. I don't think that he's 6 weeks if he doesn't have teeth. Missy had teeth when I got her at 7 weeks of age. Your puppy is going to need extra care whether it be 6 weeks or less. I would start researching about hypoglycemia (low blood sugar) and pick up a tube of Nutrical to treat him if need be. This is the problem that I had with Missy after getting her at 7 weeks of age, and it's SCAREY. I know the Nutrical saved her life. You can lose them in an instant. As far as feeding a puppy that young, hopefully the other more experienced members will come along to offer you some advice. It will be important that this puppy eats often. Good Luck! Please post pics when you can.