Q. Has vomitted on and off all day and is very lethargic.
DR. CHRISTIE LONG, D.V.M., C.V.A.
A. This could certainly be a lot of things, but in very young puppies such as yours I worry about infectious problems, such as parasites or parvo virus, as well as foreign body ingestions (because puppies like to chew on things). I strongly recommend that you seek veterinary care as soon as possible, as continued fluid loss in very young animals is dangerous. He needs diagnostics in order to determine what's going on, and then appropriate treatment.