I see. So you are saying self-contradictory things about your relationship to the current man. You saying that you have "some" connection to him but not as nearly much as should be, and yet that you have been together for 5 years, that you plan to marry him soon, and that you love each other and get pleasure from emotional bonding. So I am a little confused as to where the feeling of a lack of connection is coming from if everything (except for maybe sex) is basically wonderful.

Regarding growing asexual with him, here is where therapy (maybe joint) would be helpful, to make sure your being the victim of abuse by step-brother, betrayal by mother, and your unfortunate early sexual experiences with men would not interfere with the sexual satisfaction with the current man whom you plan to marry.