Conflicted love life

So I’ve been with my fiancé for 3 years now (4 in may) and we’re great together. I’ve never felt the way I do about her for anyone else ever. That being said, I find it strange that in my everyday life I constantly find myself crushing over other women I meet. I never make any advances and try to cheat because I’ve cheated and been cheated on in past relationships. It’s not smart. I know I’m my head that this other woman isn’t any where close to my actual fiancé but I still seem to always “catch feelings” as some would say.