4 year old Shih Tzu now refuses to walk on leash. We took him with us to visit the grandchildren. He started refusing to walk on the leash with my grandaughter. They have a labrador and our dog was not taking too kindly to when the lab came near him. He would bark at the lab. Now he acts like he is afraid of everything. Can anyone give me some answer as to what might be wrong with him ? He is acting like he is tramatized