My 7 week old puppy had a parvo shot and now just lays around and 3rd day won't eat, throws up what little we can get him to eat . I don't know what to do.

You should contact your vet. It could be that your pup has had a reaction to the shot, or it could be that he has parvo (parvo takes a series of 3 shots in the first 6 months before the pup is fully immunized against it).