Whenever I put Chloe on the leash she acts like she can't walk. She firmly plants her feet and butt and absolutely will not walk a single step. She's 11 weeks old, so is she just too young or is this the beginning of a problem? She has both a collar and a harness and she seems to be ok when she's wearing either of those around the apartment without the leash. She just acts this way when I put the leash on her. I don't want to drag her because I'm afraid that will just make her terrified of the leash, but I really don't know what to do. Any advice? Thanks!