Welcome to the rollercoaster ride!
I was also started on 100mcg of Thyroxine.
From my experience starting that high was plain awful
I was a wreck.
I experienced terrible symptoms but the headaches and eye pain were the worst....my advice is not to just put up with it like I did.
Go back to your doctor straight away,if your not feeling well.
My THS was so suppressed it was 0
I was then put on 50mcg for two months and have now just gone up to 75mcg.
Still waiting to find my miracle dose and a good doctor