Really sorry hun but I'd definately check for other symptoms and see, or at least speak to a vet.
Keep an eye on his drinking and, if you can, his toileting (amount of wee/consistency of stools if he uses his tray). I'm not going to say what it could be a symptom of as it's probably nothing but please please keep an eye on him for a few days.
The attempting to go behind the tray is because he doesn't want to use the tray. Again, this could be for several reasons, an infection-thus some pain when going or simply a smell or noise that he's taken a dislike to.
How old is Clapton? Does he have any health problems that you know of?
So sorry Mark, really not trying to scare you