My Gf (21F) and I (22M) have been together for 5.5 years and been living together for 1.5. We have always been really close and affectionate, constantly kissing, hugging, reaching for each other's hand, etc... and we both love each other dearly.

However, due to her personality, she has always suffered the dread of "missing out" on things, in various areas of her life. About 8 months ago we had a big talk and she confessed that she had been thinking about non-monogamy for a few years. She's my second gf and first sexual partner, while I've been her first in everything. At the time of the announcement, I was completely distraught. We talked a lot, and she told me that her primary reason for this arrangement is to feel completely free when we are not together. She highly values the time we spend together, but wants to be independent and live without chains when we're apart She hates it when things in her life become monotonous and stay the same over a long period of time. Also, she is anxious about missing out on her youth.

I researched the subject in addition to reading testimonies from this subreddit and others. In the end I found the idea interesting and even exciting, so I said we could try and we talked some more. Until now none of us had done anything to actively seek other partners.

Fast forward to last Sunday, when she told me that the night before she went to a bar with some friends and talked for hours with a guy friend of a friend. He then accompanied her back in front of her mom's apartment and they kissed. She said she didn't believe it would lead to anything serious, but they still planned to meet again the following Friday to go to a protest together, which they did.

When she told me that, I smile on the outside, but my heart imploded. I think I was genuinely happy for her in some way, but the storm of emotions was just overwhelming. Now I've been spending the last 7 days thinking about it literally all day. I think I was also particularly shaken because it was sudden and happened over a single evening.

I just don't know what to do. She explained that she isn't really interested in developing emotional relationships with multiple people, but at the same time she doesn't seek purely physical relationships. She wants to discover new people, see how they live, enter new social circles, just be free and not feel trapped in a monogamous relationship.

The other night we talked for a few hours in bed and I explained my feelings and fears. She seemed receptive and respectful of what I had to say, but she was left quite unsettled by the discussion, even though she was happy we could talk with honesty.

She said that if I wanted to put our "contract" on hold, she would be able to endure it but would have to mourn her loss of freedom. From what I understood, it is also likely that this would set off kind of a time bomb on our relationship because one day she will probably feel too constrained for too long.

As I've said, I find the theory quite appealing and I believe it could prove beneficial and enriching for both of us. But emotionally I've been a wreck this week. Upon reflection, I think that I could handle her flirting and maybe making out with other people, but any kind of sexual interaction seems way to terrifying at the moment. Probably, in part, because she has a way lower libido than me and it would make me insecure to know she's willing to sleep with another man even though she isn't a very sexual person and I myself struggle to be satisfied. Would it even work to put into place an open relationship without allowing sex, at least for some time? From her side, she thinks she is perfectly capable of separating the place I hold in her heart from her more casual relationships. She also doesn't think to be jealous and would see my adventures more like gossip.

Since we are currently away from each other from three days, we concluded that we would both reflect on the discussion and have another one when we see each other again. Regardless of the answer, she also wants to decide whether to stop seeing the other guy since she knows it hurts me at the moment.

Ultimately, I don't fundamentally need multiple partners, but the lifestyle does intrigue me. Also I reckon that if I want to ever live durably that way, I will have to go through what I'm going through right now. It just sucks so much.

I don't have a specific question but would be grateful for any advice. Thank you for having read my story

TL;DR My girlfriend of 5.5 years kissed another guy for the first time in our recently opened relationship. It's less about the love or the sex than it is being free to do what she wants and be independent when the two of us are apart. I feel like shit because of this situation, but I will also feel like shit if she makes concessions in order to protect me, particularly if it implies the possible decline of our relationship. I don't know what to do.