Sounds stupid, but I'm serious. Every since I can remember my energy level has been low. I can drink a ton of coffee and still feel lethargic. Caffeine will sometimes give me a short burst of energy but never a sustained boost. Even when I get a "normal" night's sleep, I still have trouble making it through the day without dying for a nap. I had blood tests done to check my thyroid, but everything seems normal on that front.
I'm a 22 year old, (seemingly) healthy male.
You are having some sort of awakening event several times per night. Sleep Medicine is a relatively new field, but there are quite a few options for trying to figure out what is going on. You may be experiencing sleep apnea, or some other sleep issue. My suggestion would be to go to a sleep specialist. They can do a sleep study to try and figure out why you are waking up. That is the best I can offer aside from you trying some over the counter sleep aids, but most of those just help you fall asleep, not help you stay asleep.
You can carry sleep 'debt' over from day to day. So if you're missing out on sleep a few days per week that adds up and makes you tired all the time.
The best way to combat this is to consciously try to get 10 hours of sleep a night a few times per week to 'pay down' that sleep debt.