My sister was just diagnosed with this (previously she was hyperthyroid and went on meds to counteract that, but now she has hashimoto's). She told me that she began noticing the difference with her energy levels improving after just a few days of taking the thyroxine. Wish I had more answers for you, but just thought I would share what she has told me about her experience.

I hope things improve for you soon & your begin to get your energy back.