Hello! I (32M) and my husband (31M) have been monogamous since we got married 3 years ago. We've talked semi-frequently in the past year about the idea of exploring outside sexual relationships, and it's something that seemed interesting to both of us, but I was hesitant because I wasn't sure how I would feel afterwards and was raised with heavy monogamous influences.

Well, this past week I was away on a trip without him and we decided it was a good time to experiment with hooking up outside of our relationship, and then we'd debrief when I returned. I communicated that I was going to try to find someone on my trip, and they said they were going to hookup with a mutual friend of ours (because they were nervous about it being a stranger). We set a list of boundaries and agreed to them.

Well, it turns out that mutual friend also invited their husband without my knowledge and it became a threesome with my partner, which I'm not super comfortable with - I didn't like to think of my husband as the outside sexual partner to this primary couple we both know, and also I wanted our first threesome to be together, something I was not clear about communicating before this week. Because of the time difference, I was asleep and my husband decided to go with it without asking me - he did not think this was breaking any of our rules but this is my fault because I wasn't clear enough.

While my experience with my hookup was mostly pleasant, I have come back and am now experiencing a wave of emotions about what took place while I was gone. I'm realizing I didn't set the boundaries I needed to be comfortable and as our first time doing this I now feel like my boundaries were violated and I don't want to do it again. I also am frustrated with my husband for changing what we talked about without getting my consent.

I don't think our mutual friends did anything wrong, and yet now I feel like I can't be around them, and I don't want my husband around them either - I feel really conflicted (and more jealous than I thought I would) when I think about what he told me they did together.

I'm trying to understand my feelings and I don't know if being open to other sexual partners isn't for me i.e. will I feel this way every time? Or could this just be an issue of needing to set clearer boundaries and stick to them while we explore this?

I'm looking for advice on where to go from here and what to do with my feelings, but also sympathy if you experienced anything similar on your journey away from monogamy. I'd also love to hear if you have advice on how we could handle this in the future in an ethical way while still validating each other's feelings and desires. Thanks y'all.