My cat Harry is usually very quiet, never meowing at all. He is laid-back, and likes to sleep, but lately that's all he's been doing. About a day ago he began to refuse to eat, only drinking water but then throwing it up later. He's become quite lazy, not moving at all. He throws up everything he drinks, and right now won't drink or eat anything. He's been meowing - or howling - at random times, and will move a little shakily. I think he can't feel his legs or something similar to that. He's also lost fur around his but and back legs. Please tell me what you think it may be, and how I can help him.