We've been working with Reesie on the leash this week, and I'm not sure how well it is working. He is 9 weeks old and does not like his leash. He is okay as long as I let him go where he wants, as soon as I put any pressure to go a different direction he hunches down and will not budge. If I can get him in motion it is okay for several steps, but then he starts grabbing the leash in his mouth and growling and snarling at it like he hates it, and starts to play tug of war with me. I don't think he is playing though, I think he is mad at the leash. What should I do??