Yes get him checked out , what is school like could there be any bullying has anything new happened recently ,new sibling, move of house ,any trauma?
Definitely should be checked out. I would also peek in on him after he has gone to bed and make sure he is really asleep and not doing something else (does he have a tv in his room, etc) .
I think you should take him to the doctor. It could be a virus or it could be more serious like something going on with his heart or cancer. Does he have any other symptoms such as legs hurting? Does he have a fever? There is something that is making him exhausted so he wants to sleep all day and you need to find out what it is.