Boyfriend is always tired

Heather
Lately my boyfriend is always tired, he sleeps more than I do and when he wakes up he complains he feel like he didn't sleep at all. This has been going on for awhile now but it's slowly getting worse and worse. It's getting to where he doesn't want to do anything at all and I'm extremely worried.
He doesn't think he's getting sick and he says he's been eating healthy, I honestly have no idea what it could be. I just really hate seeing him like this, I'm worried.