Thanks for all of your responses.
I actually take antidepressants and have done so for years now. I've also switched to different types, gone completely off them, etc to no avail.
I've thought about getting a sleep test done. I've considered the fact that maybe I have sleep apnea. I've also read a lot about chronic fatigue syndrome... and I know that can pop up later in life if you've had something like mono, etc. And I had a bad case of mono when I was a little girl and had to be hospitalized.
At this point I just want an answer.