Hi I have a 13 week old Labrador pup and he will not walk when we take him out. He runs round the house and garden but as soon as he's put on the lead and taken for a walk he plants his bum firmly on the pavement. So much so we haven't taken him out for the last three days as we are at a loss for what to do, we end up dragging/carrying him along the walk. Going to take him out today but wanted some advice/tips on how to get him to walk?