Oh, Suz, this is distressing to hear that your little kitty is not feeling well, out of sorts and can't explain why. I agree with Marley, the cat whisperer, that your kitty should be examined sooner than later.
Perhaps, he ingested something foreign into his system, when he was outside, or he has a puncture wound that isn't visible to humans. Your vet may be able to do some tests to find out why the little one is not himself and acting with such different behavior.
We, too, take our cats to their own room at night, so everyone sleeps better. You are naturally an observant person, as a writer and the Mom of a feline, so picking up on these behaviors, which are not standard and usual for him, is a good way to begin to diagnose that something is amiss. I'm hoping he'll be back to himself again very soon. xxx ^_^