Thanks so much everyone! To answer some of the questions:
This has been an ongoing problem for me. I remember when I was a teen I would sleep in till noon on weekends. I've been depressed a lot of my life and my coping mechanism was to sleep. And then, when I was drinking, I would be so exhausted the day after. So this has been going on for quite some time. I just have always loved sleep and never had trouble sleeping, could do it for hours and hours. And then I would still feel tired when I woke up, and throughout the day sometimes too. I do tend to go to sleep pretty late though. I think the only time I'm not able to sleep is like early evening. I have to wait until at least 10, and most of the time I'll wait until 1 or so.
My eating habits are healthy except I'm not able to eat enough sometimes because I'm sleeping too much, and I do exercise occasionally. I have no trouble sleeping once I'm actually asleep at all.
Yesterday, I slept the ENTIRE day - woke up at 11am and then went back to sleep from about 3pm to 9pm, and then didn't wake up the next day till like 12pm.
To be fair I was sick, I usually don't sleep through the day, but the point is is that I fully well, easily, could, I just force myself to wake up. During the day I'm usually okay and not exhausted, but sometimes it'll hit me around 4pm or so, and I'll drink some caffeine but not much. I just normally feel a little tired always though, like it's hard for me to feel full of energy.