I know that sleep apnea can cause people to sleep a long time and not wake up refreshed. I know a couple people who treat it with a sleep mask, and one person who had surgery for it. This is usually diagnosed with a sleep study.

I know that thyroid problems can result in fatigue, but I don't know if they can result in lots of sleeping. That's something where guidelines as to what should be treatable seem to have changed in recent years, and that can be checked by a blood test. (Though if you've seen a doctor in the last few years, they've probably checked that.)

Or, maybe you just need a lot of sleep.