Navigating Opening up a Relationship

Hi everyone (using a throwaway account), Was hoping to maybe get some advice about my situation. I’ve (F22, bisexual) currently been in a relationship with my boyfriend (M28, bisexual) for about a year, and the topic of nonmonogamy has come up frequently. We’d agreed on monogamy and he said he’d try his best. It came up as a serious conversation when he told me he’d been messaging men on Reddit and strongly desired sexual experiences with other people. I felt blindsided in the moment as it went against what we’d agreed on, but I wanted to accept him and who he is so we talked at length about what I would be comfortable with. Initially I wanted to shut it all down as I’ve had bad experiences with nonmonogamy in the past, and honestly it’s just not something I’ve ever wanted. We agreed about a month ago that I was comfortable with him pursuing experiences with only other men, and thus far it’s only been over the phone, nothing in person. The biggest thing was that I want to be in the loop about everything, not necessarily reading every message he sends but knowing what he’s pursing and what’s going on. He agreed to this, but didn’t bring anything up with me in these last few weeks so I assumed things were a bit dry.

(Maybe also worth mentioning as an aside, he has said a few times he views hyper sexuality as his “drug of choice” when craving escapism and pleasure. Not sure how to feel about that as we are currently going through a stressful time trying to find a new living situation and so these desires come up more when things are harder in our/his life)

A few days ago (after I prompted him as I felt he was keeping things from me) he told me he’s been messaging couples as it’s the fantasy he’s currently wanting to explore. I felt completely blindsided as I had specifically said I wasn’t comfortable with him doing sexual things with women, but also that he hadn’t communicated this with me at all that his focus has shifted away from just men. He thought it was only single women I had a problem with. I suspect he still feels an element of shame about this side of himself and still feels hesitancy sharing with me, or fearing me slowing down his desires.

There’s a part of me that feels if this is going to be an aspect in our relationship I want to at least know what’s going on, or participate myself. It’s brought up feelings of exclusion in me (and obviously insecurity), so I’ve been talking with him and contemplating it being a shared endeavour. He is all for us exploring it together, he thinks it could be fulfilling for us to approach it as a team. The thing about that is, if he wasn’t wanting this I’d have no interest or desire in pursing it. I feel potentially open to it, but there’s a lot of unease in me about it. I feel I can’t properly decide how I feel about the prospect of us doing threesomes or more together because I keep feeling blindsided and kept out of the loop. I feel quite possessive and jealous about the prospect of him with other women, and I wonder if it’s unfair for me to want to be the only woman he touches/receives pleasure from? In another part of my mind, I see an opportunity to explore my bisexuality but worry it will be clouded by jealousy.

If anyone has any advice about pursing things together with your partner, navigating this delicate and tricky path, how you go about communicating effectively, understanding if your unease is rooted in insecurity or if you just don’t want nonmonogamy, I’d really appreciate it :)