If it is so common, why does no one talk about it?
Because, more often then not, victims feel like you do. However, you are brave in bringing it forward, and, look, people opened up to that and shared with you their own feelings of shame. This is a positive thing. Please give yourself love for that brave gesture.
Now, after reading everyone's responses, I, too have something to add. I suffer from an autonomic system disorder. For those that do not know what that is, that is the background controls for blood pressure, etc. All those things you don't have to think about doing, like your heart beating. What it sounds like to me is your body reacted without your thinking about it. Just like your heart beats without your thought.
That being said, and forgive me for being blunt, but if people were able to control their orgasms don't you think people would walk around having them left and right? There would be no books out there explaining how to push the right button. No lotions, no magical tools, no partners. This was not something you could control. Your body did not really betray you, the abuser did.
Your body is this amazing thing. It is capable of doing some wonderful things, and I am not discussing sex here. It took me a long time to get to that point in realizing that. When I was in my teens I would sit in front of a mirror naked as I got ready to go somewhere. I vowed that I would not fill shame or dirty because of my body. This does not mean that I haven't gone through some tremendous pain to accomplish that. Doesn't even mean that I am totally comfortable with myself 100 percent of the time. Sex and touch, in itself, are still difficult for me. I am trying not to let the abuser win. We are all a work in progress.
I am not belittling your feelings. I think your opening up is an amazingly brave thing for you to do. I think your therapist will think the same. In fact, I believe that all of us who bare our lives and fears on here deserve a standing ovation. Without all of you I would be left feeling alone in my own darkness. You have all shown me, no matter where you are in your recovery, courage and tenacity. You have all given me hope. I wish I could give the same to all of you.