Hmm...
Gang banged without your knowlegde, permission or participation.
Sending nudes of YOU without your knowledge...
Having guys call in the middle of the night for phone sex...
Continually having sex chats online...
When you ask if she has cheated, which time do you mean? If it is not with you then IMO, she has cheated.
We got into swinging to enhance OUR sex life, not hers, not mine.
From what I understand, swinging should be considered a partnership decision (like any other joint-choice: finances, large purchases, child rearing) and considerations must be met for both sides.
If you have asked her not to continue but she still does - I don't think you have over reacted. I think you both need to take a serious look at your relationship and get some things straight before it becomes to damaged to repair.
I can see how this has caused some trust issues.