why would my 17 week old pekingnese pull his hair very hard on the outside of his legs?

Answer 1

He may have a mat that is bothering him, he may have allergies to something or may need a good brushing. Pekes need a lot of coat care. Try brushing him and see if it helps. If not, take him to the vet and have it checked out.
I love the breed.

Answer 2

he may have allegies that are making him itch, or there could be bug bites - have the vet check to see if there's any skin irritation and get it treated! Poor little guy must be miserable, if this was a child you'd try to get help, right? Animals depend on us to take care of them and know when something's wrong because they can't tell us.