What's wrong with my dog?

What does it mean when my dog began to shake excessively and when I pet him near his tail he bit me? When I went to examine the area he became very stiff.

Hmm, is there any smell coming from his backside? It could be that he needs his anal glands expressed, which a vet can easily do. Anytime a dog has his tail between his legs, it means discomfort – call your vet ASAP. Poor thing :(

I would say he is in pain…perhaps from his hips…or Labs are prone to “cold-tail”, …which is a malady that is painful, but they get over on their own.

http://dogtime.com/dog-breeds/labrador-retriever/health

Cold Tail: Cold tail is a benign, though painful condition common to Labs and other retrievers. Also caused limber tail, it caused the dog’s tail to go limp. The dog may bite at the tail. It isn’t cause for alarm, and usually goes away on its own in a few days. It is thought to be a problem with the muscles between the vertebrae in the tail.

One thing for sure…about the only thing that can depress a well-cared for dog is pain…so yes…take him into the Vets, and get a wellness check up.

when a dog has his tail down that means he doesnt feel safe! I would try and make him feel alittle more comfortable and happier! try playing with him with his toys and just let him lay by you! he probably just wants to be by you right now if he doesnt feel safe.