Most dogs will listen when they feel your the pack leader. Maybe you could read: Be The Pack Leader by Ceasar Millan you can find out more about that here: www.cesarmillaninc.com
It could be round or hook worms the dog needs to get to a vet fast worms if left untreated could cause Health Concerns.
More Than likely your dog has hip dysplasia take him to the vet right away he is in great pain.
