Extreme Fatigue For 2 Years Causes Of Extreme Fatigue?

Causes of extreme fatigue? - extreme fatigue for 2 years

I am constantly tired, no matter who from the heights of sleep. I tried to get different lengths of sleep when I sleep much / little. I slept for 12 hours without waking up!
I am looking in the chronic fatigue syndrome or anemia may, and I will try to eat more iron and folic acid to see if it helps. Is there something else that might be?
PS This is not something soon, I felt the same thing for about 2 years, so I do not think it could be stress.