It sounds as if your body has adjusted to yoru current activity level/calorie level, which is indicated by the drop in your temperature (thyroid slowing down as your body's natural defense mechanism to "stop wasting away")

An ECA would be a good choice here. When your temp slows again, add some thyroid boosting supplements to the mix (guggul & phosphates ... there is a product that combines an ECA with the thryroid boosters .... I think it is made by MHP, but the name escapes me .. Thyro-Stack, Thyrolean, something to that effect ...