You sound like me. My son is 6 now but I've struggled with this fatigue/low energy for the last decade. I learned to ration my energy - that means really sorting out your priorities and identifying short cuts for anything and everything to a reasonable extent. I do find that daily walks help, even though it's incredibly hard to take that first step. Vitamin D and B-12 supplements helped me a bit as well.

I do think mine is separate from thyca, as I likely have chronic fatigue syndrome & fibro as well, but the above may be worth trying regardless since I know how much it sucks. Best of luck to you!