Hello I just read your query and from what you have mentioned it appears that you have hypothyroidism
that is managed with Levothyroxine
It takes some time for the fatigue
and symptoms to disappear.
I would suggest that you have your vitamin D levels checked and start exercising atleast 30 minutes daily.
You can take multivitamin
tablets as well as it helps with hypothyroidism symptoms.
Hope you find my advice of some benefit and Good luck.