Mate I feel with you, but don't you think this is more of a PM thing?
I don't know you, but as for the relationship with the girl, don't get too attached, it's just a woman, don't take it personally, that's the most important thing. When I was with this woman I was in love with her but I still hit on other women. If you lose her for ANY reason, just get over it it's life, it's painful but that's it, I've done my time I know.
You gotta be Buddha on this. As for mates doing your girl that's another story, some dark force shit IMO, but what did you expect? You host a fucking Penis Enlargement convention, full of horny fucks, and no offence, but what kind of women would want to take part actively? It's no surprise if you ask me, some guys can't help it. If I was at a hot women convention with my girlfriend I'd love a foursome with 3 other new hot women than my hot girlfriend. We're humans, we're animals, men and women, you seem to be forgetting some facts man.