A medical check up is a good idea. Thyroid problems cause fatigue. Deficiencies do too. So do sleep disorders. As well as more serious conditions.

I looked into all of that because my fatigue was so bad that I was feeling like I would not be able to function at what I had to do and my depression became overwhelming. I shifted to a med that is an unusual stimulant (Provigil) and it restored some energy. Now I'm able to function better and try to do other things, like eat right, and exercise to also improve my energy level.