First have your B12 checked. If that is OK.

Make sure you are getting rest which means a good, deep sleep with no disruption.

If you are still fatiqued. I suggest Provigil. There has been recent updates that this drug may cause depression but with any drug comes side effects.

I've been taking Provigil for several years, now I can stay awake all day without the need to sleep every two hours and still be exhausted.