Rape is not a scheduled appointment with reminders . Are you perhaps fantasizing about simply having sex with him, without the factor of being forced?

At any rate, since I cannot comprehend rape fantasies, I probably should not be asking. But seriously, maybe you are fantasizing about consensual incest, Ancient Egypt-style? I think it is worth thinking along those lines, because if you now feel that the fantasy is abnormal due to two factors - rape and incest - and you move towards a consensual incest fantasy, one of the factors that make it abnormal for you would go away, and that would be an incremental positive change.