I have had the same problem recently. I have hypothyroidism and my meds were lowered in June. I recently quit taking my HRT because I hate taking meds in less I absolutely have to and am wondering if that is the problem. So it could be a change in your system. If your Dr. is paleo friendly ask him/her for a full thyroid panel not just the normal TS4. I can't remember all the terms but I can find them if you need.
You know all those things you wanted to do: You should go do them.
SW 215 lbs
CW 180 lbs (whole foods/primal eating)
LW 172 lbs
GW 125ish lbs