All sexual fantasies which are not about harming others (e.g. child abuse) should be considered normal. Please see a psychotherapist about your history of abuse
I think it is pretty normal to fantasize about a sexual scenario not involving oneself in it. While I cannot talk from the perspective of sexual abuse, i thin k it sounds alright generally speaking too, so it should be ok in your case too.
I can understand about the trigger part, but maybe some therapy might help you?