Cat Behavior changes.

My cat's name is Boots, we found him around the year 2000 or 2001 playing in the leaves in our front yard. I was about 7 or 8 and I am 21 now. Very recently my cats behavior has changed rather drastically. He normally sleeps on the kitchen chair or downstairs on the bed. As of recently he started to become VERY VERY clingy to me. Which is not a bad thing however it was a VERY sudden change in his behavior. A lot of times he would never want to sit on my lap or anything of that nature.

But now he is so clingy it's kind of annoying. I know that sounded horrible, I don't have a problem with it and I love he is so loving all of a sudden but the change happened so fast. Now for the disturbing part to me at least. He is now sleeping in the weirdest places. It started with him sleeping right in front of me on my computer table almost on the key board. Then he began sleeping on the kitchen table which he has NEVER done. And the most troubling to me is he is starting to sleep on TOP of the stove. Right on the burners. He also has been sleeping near the water bowl for a while. As far as I know his stool is normal and knows where the litter box is. He also eats and drinks normally. I just want some professional advice. 

When was the last time Boots was thoroughly examined by a vet? Any sudden behavioral changes can be an indication of a (developing) health problem. At his age, his kidney, thryoid, etc., values should be checked out.

It's been years. We're going to take him tomorrow.

I hope all goes well with his check up!