I can give you some thoughts as to why this is happening.
I had something similar to this dream. I dreamed that I was being raped, and I just quit resisting and gave in, and let it happen (no body feelings in this dream). This was because I didn't want to get beat up in the dream and figured if I just let it happen then the guy would like me and I wouldn't be beat up. Also, I thought he wouldn't try to rape me in the future if we became friends. There was a feeling that I wanted to make him (I don't know who he was) happy and be his friend. I think on a subconscious level we all want to be accepted and liked even by people who hurt us.
In dream land our inhibitions are lowered and we are likely to do all types of things that we normally wouldn't do while awake.
So maybe you want to quit fighting the thoughts of abuse while awake, and just let it go (accept it) and this is how it is revealing itself through your dream. Of course your going to think "yuck" when you wake because your waking mind is different than your dreaming mind.
I think your learning to let it go in waking life and therefore you let it happen while dreaming. It's not such a big issue to you anymore. But the dreams are freaking you out which will make it a big issue again if you let it. Don't do this to yourself! It doesn't have to be like this. Your not doing it while awake so why get all worked up over a dream that doesn't mean what it says or shows?
Please remember that dreams are not literal. I deal with these horrible images too, but I know they don't mean what I see. Even if I can't figure the dream out I just let it go because if I dwell on it, then it will produce more bad images and cause me to have nightmares.
So I don't dwell on it and as a result I don't have many bad dreams or nightmares anymore (I barely remember one dream a weak and it's not a bad image, just stupid stuff). I know it's easier said than done, but once you really understand that these dreams are a symptom of your abuse like hyperviglance, stress, flash backs insecurities etc then maybe you can just say, "OK this is just another symptom like all of the others, and accept it, then let it go"
I hope I answered your question? If not, then I'm not sure.
Take care
Tammy