fiancee wants anal even though he knows it hurts me.

im not sure what to do or how to feel about this situation. my fiancee is infatuated/obsessed with my butt and constantly brings up anal or tries touching me there during sex even though its a major turnoff for me. we have done it bc i have a hard time telling him no but even when i express my displeasure with the idea and his actions he apologizes and says he doesnt want to hurt me but constantly asks/tries. it becomes an uncomfortable subject for me and i often give in bc i dont want to ruin the mood (im a people pleaser). im just simply not into it and i fear that it may become a deeper issue. we have had serious conversations about it and nothing seems to change.. we get married in less than 20 days.