I agree with Tina and Bob. Sounds to me like you really need to talk. My ex-GF of 5 years and I always fantasized about MFM's during sex and it was fantastic. Then last year, all of a sudden we ended up with a few FMF's with her best friend. Which was great but then the best friend started hitting on me when the GF wasn't looking. Extremely uncomfortable! My GF and I ended up breaking up in Feb after my frustrations with her. We had agreed to be up front with each other and if she had wanted a MFM I was all up for it. That's what my excitement was in, but as she had a drinking problem she ended up messing around with strange guys at the bar, apparently thinking that it was her right since we had had a FMF with her girlfriend. I just didn't want to be exposed to anything she was being exposed to and her dishonesty was not something I wanted in a relationship. So, just make sure you talk, talk, talk, talk, talk, listen, listen, listen, listen, listen, and understand, understand, understand, understand, before doing anything..!