Have you taken you dog to the vet for its deworming yet???
What breed of dog is he? How did he act before this? Has he lost weight? Does he respond when you speak to him? Has his behavior changed, aside from the sleeping.
I think you should take him to a vet and have him looked at. It doesn't sound like teething but every dog is different. A vet can give you more accurate information.
lonewolf