I always thought that poor sleep and night sweats (jittery feelings/heart pounding) were associated with being HYPER, but when I tested HYPO 6 weeks ago, I too was experiencing the same stuff along with the muscle weakness and nausea (heartburn too) that you are describing. I thought it weird that I had a body that wants to rebel & mimic symptoms that are opposite than told to expect! I guess that means we are normal?! Well I get my blood tested this week, and meet with the endo next week. The good news is that I’ve being feeling better the last couple of weeks, so once your dose is increased you should feel better too within 3-4 weeks of starting it.