Chi whines incessantly all night long

My chi will be 10 in December. Throughout his entire life, he has slept burrowed under the covers in bed. About three or four months ago, he would jump off the bed as soon as we turned the light off and go sleep on the floor in the bathroom. Now, in the past three weeks or so, as soon as the light goes off and we go to sleep, he whines INCESSANTLY throughout the entire night. We have tried everything: keeping a light on for him, keeping the TV on, feeding him, walking him in the middle of the night, giving him extra exercise during the day, bringing him back in bed cuddling him, petting him, throwing toys for him in the middle of the night. NOTHING WORKS. I get out of bed and bring him back into my bed literally 10-15 times during the night, only to have him jump off the bed 90 seconds later. He has no interest in chew toys, so that's not an option. He's never confined to a crate and has full run of the house.

I'm planning on taking him to the vet, but I really don't believe there is anything physically wrong with him as the only time he behaves like this is at night. It seems to be some type of anxiety, but I have no idea what could be causing it, or how to stop it. I really don't want to sedate him.

There haven't been any major (or minor) changes in his life or routine recently.

Anybody have any experience with this? Feedback/thoughts/ideas would be greatly appreciated.

We've only been able to get 2-3 hours of sleep at night lately because of his carrying on.