I also had pain free periods but I’ve always had a weird pain in my thighs constantly and legs, not agony but a weird feeling I put it down to growing pains / everyone must feel like this. I would notice after a lot of walking my legs would ache a lot and I put this to being lazy. It’s like a weird vibration in the legs / thighs and pelvis like something is on the nerves, it’s more of a weird feeling then painful if that makes any sense, so hard to describe. It’s been for years and I would describe it as unusual than unpleasant, gradually it has become worse over time, feeling it today really feeling it in my legs today, such a weird disease!
Maybe my pain tolerance is high as I never thought anything of the leg feeling and just thought it was a human thing haha