RLM what you may have is a candida induced case of functional hyppthyroidism. Your body has PLENTY of t3 and t4. But because of the candida, your body is unable to use the t3 and t4. Think of type II diabetes. A type II diabetic has PLENTY of insulin. But the cells of a type II diabetic have developed what is called insulin resistance.
I had the same thing, always cold, low body temp. I felt absolutely miserable. My thyroid panels always came back normal. It took four tries, but I finally found a MD that would prescibe Synthoid for me, I felt a great deal better.
When I was able to control the candia, my hypothyroidism symptoms disappeaerd, and went off Synthoid.