HORMONES!
As oestrogen levels drop muscles may become lax = aches and pains. As suggested, a woman' physio should be able to give advice.
Do read the threads about vaginal atrophy. Important to be ahead of that one!
Check your posture when sitting: typing, watching TV, driving; also your foot wear which can impact hugely on posture = back pain. Gentle regular exercise is good we have several threads on exercise/cycling/swimming etc..