Cat lethargic, not eating, hiding, acting strange...HELP!?

It sounds like to me, that he has bladder crystals, low position to the ground and wondering places he normally doesn't go and talking a lot. I wouldn't wait to take him to the vet, I would take him now. If I am right this can kill him in a short amount of time. My cat acted like this when he had bladder crystals. He is actually straining to pee, so he is looking for a better spot. TAKE HIM NOW, better safe than sorry.