Low Core Temp.

I've been having a problem with low core temp/circulation issues for a couple years, now. Today, when i left to go shopping on my bicycle, my temp was 97.0. When I came back, it was 95.6. I rode 4 miles, picked up 40 pounds of groceries, put them in my pack, and rode back. This was in 75 degree weather, full sunshine
I have heard that Lugols 5% Iodine might help. I have had a saliva cortisol test done, and I have a normal diurnal curve with normal but low levels of cortisol, testoserone, etc.
Do you think it might just be my thyroid?

Paul