My cat hasn't eaten for 1 1/2 days and isn't active at all. He has vomited 3 times aince then. He is very lethargic and won't even jump up on my lap. Just 30 minutes ago I heard him howl downstairs...and found him laying down. I inspected him and felt around and he doesn't appear to have any physical injuries. What could be wrong? Should I take him to a vet ASAP?

