My fiance says my vagina is loose every once in a while i'm no cheater at all. i have pcos/ insulin resistance and i've tried explaining how a woman's body constantly changes. how can i get him to understand this doesn't come from cheating?

Vaginal changes: The vagina is a potential space that expands and contracts based upon sexual responses,, estrogen presence, and childbirth passages. The fact that your fiance's response was "cheating" shows a lack of knowledge of female anatomy and physiology. If this is your "forever knight in shining armor", a "re-think" of this relationship for the future is in order.