Any unexpected bleeding should be inspected. I believe that the Mirena can cause bleeding initially, hopefully someone will be along with knowledge. You could put 'mirena coil' into the search box to see what pops up.
Hysterectomy is a HUGE operation, major surgery. Do discuss HRT options prior to any intervention, because many surgeons simply don't have any idea as to how hysterectomy affects women.
Do U feel supported?