Michael,
Hang in there. It sounds like you are active and look after yourself which is the best treatment for fatigue. Even if the thyroid test is an issue you may want to consider taking a daily multivitamin it may help. Evalute your fluid intake are you keeping hydrated? Fatigue can be caused by even slight dehydration so it is important to drink plenty of fluids.
When you feel tired rest, it is not uncommon even a year or more after chemo and radiation for your body to still be feeling the effects. A 20 minute rest even if you don't sleep can do wonders and recharge your batteries.

I hope this is useful.

Mike