Sometimes when im with my fiance and he starts to show sexual interest in me i feel scared, i feel objectified, i start getting upset and ask him to stop, as if i feel threatened

He has never hurt me, hes always respectful and im attracted to him, when im turned on the story ends different, but sometimes i feel as if a trigger activates in me and i feel in danger, i feel scared to be looked at sexually

This ofc affects us bc he never knows how im gonna react, or why i react liek this sometimes.

I dont recall any sexual abuse or harassment from anyone ever, so i dont know if something could have happened to me and i dont remember? Or where could this come from