I wouldn't bath him at seven weeks. Why do you feel he has to be ? Does he have fleas ?

Tick

No but he smells

Bathing Puppies for the First Bath (http://www.petbitsforyou.com/bathing.html)

7 weeks is very young, I am crossing my fingers this puppy was a rescue and not purchased.

I bath puppies just in a baby shampoo. Regular dog shampoos are a little too harsh on their skin at this age.
You can buy special puppy shampoos from pet stores and even some supermarkets sell them.

What sort of temperature is it where you live and what breed?

Dawn dish soap is very gentle too. Just a TINY drop will do. Is the mother around to help keep the pup clean? I'm with Shazzy on asking where and what breed?