Rapid Health Decline

[lothlorien317]

I own a five-year-old Bichon Frise/Toy Poodle mix. He has been fine (aside from swift onset cataracts in both eyes) until a few days ago, when he suddenly began to rapidly decline. He doesn't seem to be able to chew (he will consume some liquids but hasn't been eating), he can hardly walk (he holds his body like he's a bear with an arched back), and he cannot be carried. Even his tail is having a hard time wagging. He yelps severely at anything pressing on his underbelly and shakes for several minutes after. He's hiding and cannot get up in the morning whereas he normally would be frantically greeting us. There's no known trauma...the first time we realized anything was wrong he yelped and his body seemed to freeze up and tremble and his jaw was clacking as he had a hard time breathing. The symptoms don't make any sense to us...can you please help? Thank you so much.