Boy, can I relate! I used to sleep 14-18 hours at night and then struggle to stay awake the rest of the time. It was so bad that I used to fall asleep at work and would take naps (even at work) when I could get one it. I know I have sleep apnea and wear a CPap at night. It only helped somewhat. Finally I went to a sleep specialist who prescribed nuvigil. I take one an day and it really keeps me awake. I now sleep 8-10 hours a night, feel alert and enthusiastic all day. I have tons more energy and I like my job again. I still have MS so I fight fatigue but that is a totally different monster.

I strongly urge you to go see a doctor. I literally gave me back my life.