I'm not a medical nor a mental health professional. So I can't offer anything substantive with regard to this. I presume you've had yourself thoroughly checked out medically. If not that would certainly be important I would think. Here are links to 2 articles, from PC's archives, that offer tips for dealing with the overwhelming fatigue of depression plus a link to an article that discusses conditions that feel like depression but aren't :

5 Tips for Dealing with the Overwhelming Fatigue of Depression

5 More Tips for Dealing with the Overwhelming Fatigue of Depression

6 Conditions that Feel Like Clinical Depression but Aren't