The one time I was seriously exhausted all the time, even though at the time I just kept thinking it was my normal exhausted all the time feeling, turns out I was extremely anemic & my OB/GYN put me on a prescription folic acid/iron supplement that I had to take 3x daily for quite an extended period of time. But this also coincided with having a uterine fibroid & endometriosis. So I guess if everything else checks out, exercise & diet are the next steps to undertake, both of which I have an exceedingly difficult time with. I hope it doesn't turn out to be something serious for you.