Hi there,
It sounds like your puppy has worms, often the itching and scooting is a classic sign. So i would check that he has been wormed recently with something like panacur or drontal.
Also it might be worth getting the vet to check his anal glands as these can become very full and uncomfortable causing them to scoot too! If he has had Diarrhoea or very soft motions the anal glands will not have emptied fully. These glands release a foul smelling substance on to the faecese basically as a territory marker.
So would Routinly worm him - and on having vaccinations get the vet to check his anal glands and hopefully that will sort the problems.
Hope you have lots of fun with your pup!
Regards
Selena Carnell VN