Mine was an iron supplement from my dr it worked really well for my sluggish moods :)
My doctor told me stretching and exercises help. I have the fatigue spells too when it gets close to dinner time I want to sleep but I'm the one who makes dinner.
I usually take our dog for a walk. I walk the dog more now that I'm pregnant to keep moving and active. Once I stop moving I will fall asleep. My 3 yr old seems to think we get up every morning at 5am so that's killing me.
Honestly I've never figured it out either. I also have a 3 year old so I have to function. I will have a small cup of coffee when I start to fall asleep. Sometimes I will randomly take a walk. It makes me push through the exhaustion.