Do you think that may suggest your symptoms are menopausal rather than letrozole?
I've done my 6 months on letrozole and sleep depraved and worn out by it all so I come off it tomorrow! yay!
I am going on to something else so I can't let you know if there's a withdrawal
Don't know of anyone having a break like you but that doesn't mean there isn't - have you used the search facility to see if you can find someone from earlier times, 2014, 2015 that may have had a break and suffered withdrawal
Otherwise all I can say is keep up the pain killers and hopefully it will subside soon!
Take care