I totally agree with you SchrodingersCat about the other guy.
First i feel concern of my girlfriend because he tends to met some pretty macho guys, I told her that she should tell him (i know it's scary because we both are new to this, and we tend to think that we have no chance to met other people that thinks like us or accept it, but the girls I met they always know i had a girl friend, I didn't know then how to say my way of thinking that's why they always were some kind of friends and there was no commitment to anything more, so I told them that my girlfriend and I had problems but we were still dating) because there's a chance that if they discover the truth they may react against her.
Second that it's true also, how can i expect honesty, when she's making that to that other guy, I used to think this was like a kind of game, and i don't think much about that kind of problems until now, and until i discovered poly. But as things get serious, I think we should put the cards on the table, because i realized that this could hurt us, and damage the relation, so I'm pursuing a more responsible way of dealing with multi-partners.
The main issue now, is that I don't know how to introspect the problem, because I'm out of control of my feelings with this jealousy thing, so I use to think that she didn't have to leave that other guy, because that could potentially make me dismiss any other future guy and that's something I don't want to do.
I don't know how o deal with this, to what extent set boundaries and when the boundaries become restrictions, somewhere I read that to explore poly the couple should be a healthy couple and be in good form, and we certainly are not so.
My requirements are, unlike other ideas i have, clear as glass: I don't want to restrict her in a way control(even if that is what i wish the most, because the jealousy hurts like hell but i don't want the easy way), I don't want to be mono even if this crisis is trying to convince my about the goodness(delusional safety) of mono.
I didn't take the step of asking her to leave that guy until be sure that's not a decision taken by jealousy. But I become more convinced everyday that we should put a pause to partnering until we fix our relation, on the other part, even if she tell me every time we talk, that he's just a game or hobby, I feel somehow that she feel something for him.