You are definitely in a complex situation, it is not as simple as 1+1=2, I think the best thing you could do for yourself is therapy and a change in social group if that is at all possible. Even with these problems the fact that you are beginning to see the issues with your own actions is a good sign, it is one of the stages of sexual abuse recovery. As for the reasons why you started this troubling behavior to begin with, I believe it could have been a way of punishing yourself, or maybe your unconscious self was disgusted by what happened and thus felt like you were now morally corrupt. It could also be that your unconscious mind was trying to reclaim your body, your sexuality, over what you had lost that night. The important thing to understand is, you are not alone in this, although I did not behave like this myself after my sexual abuse, I do know several, several women and even a man who acted in the same/similar manner until a couple of them got the proper help and support they needed, they are survivors and you are too. Getting the love and support you need from good people is the most important thing you need, I really hope you have a good support system and can open up to them at some point about this, that will help you heal faster than anything else, and none of it was your fault, you need to take that to heart and keep it there, it wasn't your fault.