I have had this as well. Sunday was horrible. I woke with a body temp of 96.6.. ice hands and feet. I could not stay awake and was under two comforters and two flannel blankets while my son and husband, kept prodding me and asking if I was alright. By 6 pm my Tp had swung to 99.8.. by bedtime I was 100.8. This morning.. 97.2.
I am on the Hashi.. hypo hyper swing ride this week. The scariest was the shutting down of my system.. and the inability to stay awake.. it reminded me of coming up from anesthesia. I am looking into this and am due to get my quarterly blood work draw up next Wednesday. If I have another day like Sunday.. I will be going in and getting the blood work drawn.. right then and there.
The bath trick works. I have used it.. unfortunately Sunday I was all over the place and a hot bath would have made it worse. I wish I had a better answer you need to have your bloodworked checked and be sure they take FT3 and FT4 next time. Your Tp is not normal and needs to be addressed. Have you checked out you OB or IM? What other symptoms besides low Tp do you have?