Originally Posted by
helplessinvan 
Why do I feel that responsibility, that guilt? I have begun to understand co-dependancy and that I am co-dependant - is that why I feel responsible and guilty?!
Yes.
We feel responsible for other people's actions, feelings, and decisions.
We have no control over them, but we feel responsible anyway.
Originally Posted by
helplessinvan logistically, it would be impossible for me to sneak in some guy, have sex with him, and have him back out in just ten minutes without my bf seeing him).
I remember a section in the "Why Does He Do That?" book, talking about how this is a form of control, to make baseless accusations. He
knows he's wrong, he knows that logically it's impossible, but he accuses anyway because he wants to control, and this is one of the methods he uses.
The example in the book was of a guy stopping by the office to go to lunch with his wife, watching from the lobby as the elevator stopped at the third floor (where she worked) before returning to the lobby. There was a man in the elevator with her, and he accused her of cheating on him
in the elevator because he "saw the look they exchanged." When asked about it in his counseling group, he admitted that he knew it was impossible, but "he had to keep her on her toes" and that's why he did it.
You might benefit from some of the posts in this book study:
http://www.soberrecovery.com/forums/...-chapters.html