I have a 1 1/2 year old lab spaniel mix. He's normally a great dog - energetic on walks even too energetic. For the past couple of days whenever I ask him to go for a walk he gets all excited but then when we get outside we cross the street and he lays down and won't budge. He usually walks fine on the leash. He seems to be acting pretty normal otherwise its just on his walks. I'm getting concerned. I think I'm going to schedule a vet appointment make sure he's completely healthy. Any advice on the sudden change?