What's wrong with my man?

We had a big argument today about him sleeping any chance he gets! He's awake 3hrs a day. Work for 8hrs, get on his computer for 1hr, watch something on TV, barely talks to me then go to sleep. His job isn't too physical. On his days off (weekends) he get up at 4pm and then the day is pretty much over and then back to bed at 9pm. He said he doesn't know why he's always tired and he's been this way since he could remember. It's tearing us apart. We never do anything together. I work 8 hrs, 5 days a week too and I come home to someone who's already asleep and can't be bothered with me ugh. We're going to the doctor next week to get some tests done. Anyone have this issue? What could it be?