Too much sleep, always feel exhausted

Patient: Hello,Over the last few weeks on many occasions, I have been getting in from work and sleeping from 7:30pm until 9 or 10 am. When I wake I don’t feel refreshed at all. I’m not motivated to do anything and I feel like I’m sleeping my life away.I have been to my doctors and had blood tests to check for anemia and thyroid problems and both were clear.What else could this be? I have been like this on and off since my late teens. Any advice would really be appreciated.Many thanksZoe