My puppy is very sick, he won't eat and he vomited his own feces does anyone know what's wrong

Take him to the vet now

I agree! He needs to go to the vet ASAP! I'm not exactly sure what you mean by vomiting his own feces. Did he eat his feces and then vomit it up? Has he had all of his puppy shots? Parvo shots being most important at this time. You NEED to have him checked out!