Exercising as much as you do might further slow down the thyroid. You're basically in starvation mode from the low calories and making it worse with the exercise. I think it's particularly bad for people with low or marginal thyroids.

Anyway, whatever changes you make to your hormones, do it VERY slowly or you're going to suffer a few weeks later if you overshoot the dose. Give it a good 4 weeks to take effect.