My (21M) boyfriend (20M) of over a year and a half have been in an open relationship since February of this year. We got off to a super rocky start---basically every mistake you can make opening a relationship, we made. We'd discussed nonmonogamy when we started dating, and we both knew that it was something that we were interested in exploring within our relationship. He's more nonmonogamous by nature (it's a necessary part of relationships for him), whereas I'm more nonmonogamous by choice (it isn't necessary for me to feel fulfilled, but it's fun; I'm naturally more jealous than him, though). Our first attempt at nonmonogamy was an impulse threesome I chickened out of, we didn't lay down good foundations for his first solo hookup, I had (and still work with) a bunch of unresolved attachment issues, I tried to set a million rules, etc. We were pretty sure our relationship was going to end, but at some point, we realized that nonmonogamy does work for us and that it's made us way better at communicating with each other.

My boyfriend's first two FWBs were also occasional FWBs of mine (the first crashed and burned when he tried to sabotage my relationship with my partner and tried to gatekeep me sleeping with a mutual friend), which involved infrequent solo hookups and me tagging in for threesomes or foursomes. I still dealt with a lot of insecurity and jealousy, but my boyfriend did a very good job of reassuring me in our relationship, and I bought books/read articles/perused this subreddit to work on my attachment issues. After a few months of work, I finally reached a place where I felt mostly comfortable and secure in how this new part of my relationship functioned.

Over the last couple of months, our relationship with the most recent FWB has fizzled out---he's still a casual friend, but the sexual component didn't seem to fit quite right anymore so none of us have pursued hooking up again lately. Since then, both my partner and I have met new people online; the one I've talked to/hooked up with (23NB) lives in our city, and my partner's new friend (21M) lives about 100km away. Both of us have hung out with our respective new FWBs a few times; I've met his twice, he's met mine once; we've both hooked up with them on our own 1-2ish times. I really like the person I've been hanging out with, and I'm really glad to have a new friend, but for me there isn't a romantic attachment underpinning the sexual attraction. They're my friend, they're hot, I like fucking around with them, I like talking to them, the end. My partner and his new FWB, however, have a super close connection forming and my partner's confirmed that he does have a crush on his friend (I'm not insecure about that, I think it's all in good fun and I'm enjoying watching him finally make new, really good friendships since the pandemic). I'm happy for him, and this is the first FWB he's had that I see him having a genuine, really cool relationship with---and I really like the guy! He's invited me to a couple of things and we send the occasional meme back and forth.

One pattern I've noticed with my partner since we opened our relationship, however, is that he gets SUPER intense NRE for weeks/months after hooking up with someone new. Again, not a problem---it's silly, it's fun, it's part of the experience. With that said, I feel like he has a hard time balancing the NRE feelings with the more stable, routine love that comes with our relationship, and a lot of the time it leaves me feeling left out or less important. He has a really hard time giving me his full attention these days because he's engaged in really good conversations with his FWB over text. He's got ADHD and he genuinely struggles with keeping his phone out of his hands when he's talking to people (this isn't an excuse, either, it frustrates him to no end and he has been working on it), but it's reaching a point where sometimes he's picking it up when I'm midsentence to start texting. I've brought this up to him a couple of times and he says he's trying, but sometimes I feel like he isn't really being mindful of it. He also hasn't been putting in as much effort with me lately---which might be attributable to us moving in together in March and our routines merging---but it's making me feel like I've been replaced with a shiny new thing. One thing I really miss from the beginning of our relationship is when he'd send me new music to listen to, but now he's making playlists for this new guy and hasn't shown me anything new in months unless I push him about it. He doesn't ask me to come sit with him on the balcony as much. He's stopped offering to roll me joints. Just... little gestures, sweet things that let me know he was thinking about me. I miss them.

I do genuinely think he isn't doing this on purpose. He has a ton of anxiety about making me feel bad in this relationship, which is why I'm coming to Reddit for advice on how to talk to him. I want him to know that I am in support of his new FWB and the NRE that comes with it, but I also want to make it clear to him that I feel like some of my needs are not being met and I would like him to show me (not just tell me) that he loves me a little more often.

I love him so much, and I value what our relationship has become. I just want to make sure I communicate this issue as clearly and delicately as possible so I don't make him feel super guilty or worried.

TIA for any advice.