I have a Chocolate Lab named Buddy. His back leg is EXTREMELY swollen. He will not use it, at all, just drags it everywhere.. it acts as if its "dead". He also has lost TONS of weight. He did have a tapeworm, but we treated him for that, but continues to lose weight. He shivers alot, and I recently noticed he has been doing this weird thing with his eyes; almost as if they are rolling in the back of his head. He seems to be always thirsty; he will drink til he throws it up again.. I NEED HELP!!