My girlfriend was the first woman I lived with, when I was a junior in college. We had a very tumultuous relationship over the next five years. We ultimately moved from Santa Barbara, CA to Madison, WI for grad school. Once there, she fucked her graduate advisor which led to the strange sexual encounter I had with our couples' counselor. But that is another story.
But, as undergrads, we led rather open and wild sexual lives. After a year living together we decided we decided to try an open relationship. We agreed to politely inform the other in advance of going on a "date" or spending the night away from home. Beyond that we also agreed not to discuss whom or what we did.
And although we were both having frequent dalliances, we still had sex together daily. Some people in open relationships find sharing stories arousing and use this to spice things up. I however, thought shared details might lead to insecurity or jealousy. I was right about that.
Despite our agreement she frequently asked me about what I did on my dates. I typically refused to provide details and reminded her that we had agreed not to discuss them. She would then say more general things like "Just tell me this... did you go down on her?" In fact, she asked that same question almost every time I had a date. I finally said "You know how much I like eating pussy. So, you can assume that I always do that." Then she changed her common question to, "Did she cum when you ate her?" I should have known this was a danger signal that would come back to haunt us later.
Once when we were at a party with a group of my pre-law, philosophy department buddies and their girlfriends, one of these women struck up a rather intimate conversation with me while my girlfriend was shooting pool. Janet complained to me about her boyfriend, who was one of my best friends in college. They lived separately and she felt he ignored her and treated her like a convenience rather than a girlfriend. She said she knew he was frequently with other women although they had agreed on monogamy. She asked me what she should do. I told her she had three logical choices, break up with him, confront him with your accusation and complaints and discuss things, or accept it as is and take on lovers of your own. I was half kidding about the last choice.
Janet responded immediately, "I like door number three. Are you interested?" She said it with no hint of irony. I replied, "Are you free tomorrow morning? I don't have class until 10am."