Seeking relationship advise
I'm a straight man and I've been in a monogamous relationship with my bisexual girlfriend for 5 months. We were each other's first boyfriend/girlfriend, we were each others first sexual partners, and I have strong emotional attachments towards her, which makes it extra-difficult for me when faced with the possibility of breaking up with her. Recently, she has developed a crush for another bisexual girl, and I'm perfectly fine with her dating other women while we're together, absolutely 0 problems whatsoever. So, she says that she wants to have an open relationship for a few months so that she can date her while we're still together. When I asked her if being in an open relationship meant that she would be allowed to date other men, she said yes, but that it was okay because I can date other women. However, I dont see myself wanting to have intimate relations with any other women than my girlfriend, except for possibly with her new girlfriend if that's something we decide to do. And I do not want to see her having intimate encounters with other men, only other women.
She says that there are no men that she's interested in right now, but if it happens in the future then it's something that we're going to have to deal with. I've asked her if there's any roles that I've been unable to fulfill and she claims that I've been the perfect boyfriend and that I'll always be her primary partner no matter what. I do a wonderful job of generously pleasuring her until she's satisfied. Unfortunately, I have suggested the idea of the "One Penis Policy", and we've been unable to compromise. We're so great together and so compatible with each other, but the mere thought of her being with another man while we're still together makes it impossible for me to maintain an erection, and if I dont break up with her before she starts dating other men then our relationship is going to be ruined regardless considering how hurt I would be (I'm already hurt knowing that she wont allow me to be her only boyfriend) and how different our sex lives will be without me being able to maintain an erection. We've given each other a week away from each other so that she can pursue the beginning of the relationship with her new female partner and so that I can spend more time deciding what I want to do. I love her and I want to stay with her until the day comes when she dates another man, but at that point I'll be too hurt by the fact that I'm not her only boyfriend that I'm going to have to break it off. I've talked to all of my poly and non-poly friends and everyone seems to mutually agree that if we cant overcome this ONE problem in our current relationship, then it wasnt meant to be. I understand that I'm a jealous person and that it's something that many poly couples have to deal with, but I refuse to accept a relationship with multiple men, I'm 100% sure that it wont work, and she's pretty stubborn about having the option available even though she's not currently interested in anyone else. Should we break up now, due to us being unable to compromise an integral part of our relationship? Or should I continue to date her (we still love each other very much) until she finds a man she wants to date, then break it off? Since she told me this is something she wants to do for a months, and she has never expressed any interest in other men while we've dated, perhaps I should continue dating her in hopes that she doesnt find a new male partner that she's interested in during that time? I'm so emotionally attached to her that it's impossible for me to leave her right now, but the pain from breaking up with her now would be less difficult than the pain that I'll feel if she finds another man she wants to date.
It's so hard for me because it took 20 years of life on this earth actively searching for that special someone until I finally met my first girlfriend. I had attractions towards women up until that point, none of which led to anything, but those were merely lust. My girlfriend is the first person for me to have fallen in deep love with. I'm worried because noone I've ever met comes even close to how I felt about her the moment I met her. As stupid as this sounds, I'm really not sure I'll ever meet anyone else like her.