Thanks for your courage to post this. I wish there were more places where people could speak freely about this. Getting pleasure from abusive relationships is a thing that is very taboo, and again, I wish more people would be talking about it. It might be a bit different, but I know that a lot of rape victims can feel pleasure (even if it is just physical) during actual rape, and can even reach orgasm. This piles up on all the other layers of trauma, because people feel that their bodies have betrayed them, belong to the perpetrator and not to them anymore, or they invalidate their own abuse because they think that if it really was abuse they would never have gotten any pleasure from it. This is why sexual abuse is even more messed up than what most people think. But when someone goes through that and don't know this about sexual abuse, they can think that they are the ones to be messed up. If only more people knew about this... But it's a vicious cycle. People don't know about it, so tend to think that it's actually people who talk about it that are messed up, which prevents even more victims from talking about it. I know people who have been through this but it isn't my case personally, so take this with a grain of salt.
Anyway, this is just something that is possible. I don't know for a fact that all victims of incest or pedophilia necessarily develop mental disorders, whether they are traumatised or not. But there are so many things that can happen. It does seem that some people can be very traumatized by rape, for example, while others will move on more easily even if it clearly was rape in both cases. There are just so many factors. Also some people can have problems and not realize they are connected in anyway with the abuse and so on... I also have a sibling who realized only around 30 that our mother's behavior was very abusive, and it is cristal clear now. When some people are used to certain standards they can also judge things by these standards. Also I believe people can be affected on the long term by something even if that thing did not cause obvious suffering when it happened. That sibling of mine, for example, had a very crapy relationship with our mother. On some level the "trauma" was not even obvious because it was just the relationship that was messed up, like mostly with poor boundaries and especially around sexuality. It's not like they were prostrated and crying when something like that happened, they rather got used to it. But this might precisely be the problem. This had long lasting consequences on their relationship with themselves with others and with their own sexuality, precisely because they have integrated a part of that relationship in their own personality and behavior. So not all traumas have to hurt. Maybe "trauma" isn't the correct word for this, but if their is another word it causes damages all the same.
In my opinion, according to the things I have heard and seen, it is ok and not so rare to feel pleasure during an act that is abusive nonetheless. This can even cause traumas in and of itself. So I would absolutely not conclude that something wasn't abusive just because it contained some elements of pleasure, quite the contrary. I wouldn't bet that one necessarily has to be deeply traumatized after such abuse, but a therapist would know better.
Also you talk about consenting and wanting it, but you also say you were between 5 and 12. I think I get what you mean, when we are kids we can want or not want things, or we can consent or not consent, but as you know it is very different from the consent of an adult. It is weirdly much easier to understand when you picture it with another kid instead of yourself. I saw a documentary about a kid (about 5) and his mother who were terribly beaten by the father, to the point that the kids life was threatened. But still, after they had to be taken appart, the kid was saying that he loved his father and missed him. Obviously kids don't function the same as we do. [TRIGGER WARNING Pedophilia] If you heard the story of a guy who tried to trick a 5 year old kid with sweets and asked him to touch his parts telling him it is ok, that it is normal for people to do that, you would clearly say that this clearly IS abuse, and that there is no excuse for that. I think the kid's consent or desires would not matter much to you (but I don't want to speak for you, let me know if I am wrong in saying this). [END OF TRIGGER WARNING]. You would probably say that the guy's acts are wrong, whatever the kid's state of mind, and you would probably say that this could have long lasting consequences on the kid's life even if he consented (but again, let me know). I am saying this because in my opinion, when we project ourselves in ourselves as kids, it is very easy to do so keeping our adult's mind and forget what it really is to be a child. I remember reading a person who had gotten through sexual abuse say that they didn't consider that what they had been through was abuse, because they didn't live it like it was abuse (perhaps this could also be a protection mechanism?), but if they saw it happen to another kid they would clearly jump and say it is abuse with no hesitation, and they found that this difference in treatment was weird. And to me, this is already the sign that abuse has left some marks, but I am not a therapist. This is just from the things I have heard.
So I haven't been through physical sexual abuse myself that I remember of, but I suffered from the poor boundaries around the sexuality of my mother. She also had incestuous words and attitudes towards me, but no physical acts and no situation I got any pleasure from. But I suffered with what I think is/was sex and love addiction, and met different people with other sexually abusive backgrounds in kinds of group therapy who could share their experiences.
But about DPDR, I thought for a while that my DPDR could be related to my mother's poor boundaries, not only around sexuality, yielding to a poorly differenciated family or bond, yielding to a poor differenciation of the self (I just discovered the name of this concept, I am not sure yet if it means what I think it means), which (I think) means the feeling that ones emotions or feelings don't really belong to them as a person, or aren't managed as such, but are kind of shared with someone else or a group... Or at least not well bound to one's identity. I think this could at least have worsen some of my addiction problems because I feel I did not learn to manage my behavior as an individual, but sort of rely too much on someone elses presence, or this kind of thing, and I maybe have a poorer way of managing my own emotions without an external substance or behavior. I feel I tend too much to go through different inner processes as if they were external things, like my own sense of responsibility, or some emotions, some aspects of my personality and so on... which I obviously relate with depersonalization. But this is only my own little personal theory at the moment.