I am 32, and I have been in a relationship with "O", who is 25, for 5 years. We have been living together for 4.5 years, and have a wonderful son aged 1 and 3 months. We are both queer/gay men, and my partner is also an FTM transman.
Our relationship has been fully monogamous only in the first year or so. After that time, we found ourselves doing a 3-way with a good friend of ours, and later with a few other people we know. While I was quite scared before the first time and only reluctantly agreed to try, I found those threesomes to be an awesome experience for me - they gave me a space which has enough safety (due to the presence of my partner) and on the other hand a great deal of excitment and discovery - both in doing things myself and in seeing my partner with other people.
I was quite satisfied with this arrangement - mostly momogamous, but with the occassionaly threesome - but unfortunately, my partner was less happy with it. While he enjoyed the threesomes they did not give him the full measure of what he wanted to experience with other people, and we repeatedly found ourselves talking about an open relationship, and later on about polyamory.
We started by taking an "open week" while my partner was abroad, and in that week I had sex with 2 friends. After that was done, however, I found myself growing more and more nervous thinking about what my partner is doing while he is away, an anxiety which grew all the way to something which felt like a panic attack. I acted in a way I am not proud of, and really gave my partner a hard time (sharing my feelings, crying over the phone, etc.). I did not ask him not to do anything, but I did not really give him the space he needed to experience things with other people. When he came home, we closed the relationship back to the mono with threesomes mode.
This was about 2.5 years ago, and since that time we have been very busy with planning and raising our new baby. Last september, however, my partner raised the issue again and after some thought, we agreed that we don't want to live in a closed relationship anymore. This was more of an ideological decision, and we did not do much about that "opening up" since then - none of us had been with other people so far, and hasn't been actively seeking to do so.
A few months ago, my partner started attending university, and befriended "F", another gay man there. It was very obvious that O was interested in more than friendship with F - at first it looked like he was interested in casual sex, and later, it seemed more like he is interested in another relationship. I find myself dealing with the first real instance of polyamory (although nothing has actually happened betweem them yet) - and feel like I am failing miserably at it. I feel sad and anxious all the time, hardly enjoy anything (even time with my kid), and obsessively thinking about this issue. I don't know what exactly bothers me - I don't feel like I own my partner, I don't think I have the right to limit his freedom, and I wholeheartedly believe that an open/polyamorous relationship is the right way to live. At the same time, I am hurt by his every word and action, feel like small and diminished, and feel like something will be lost in our relationship once my partner progresses with this new relationship.
I really want to find a way to support my partner in this and to truly give him what he wants, and I'll be happy to hear thoughts and experiences from others...