How can I (26M) be more comfortable in LDR when it feels like my fiancé’s (36M) eyes are always wandering?

We have been together for nearly three years and were recently engaged as of this summer, and beyond some of (what originally felt) as me being anxious or paranoid, our relationship is perfect. He is encouraging, loving and pretty much everything I could ask for in a partner. He has his own issues with anxiety and mental health, and due to that we have always tried to be as up front and open as possible whenever we are having negative emotions about something one of us did. I am pretty much the polar opposite in personality to him. Where he is talkative, outgoing, and wants to be doing something 24/7, I prefer my life to be a little calmer and quieter. None of this was ever an issue or bothered either of us and our relationship has always been problem free. From the time we started dating, he has always been honest including about the fact he is friends with many of his ex-hookups or people he had been in relationships with. That I found a little unconventional and unique, but not something I had an issue with either.

We are currently long distance due to work/school related matters and his previous appreciation of others' appearances (talking about how certain actors/actresses are attractive, or what he found attractive in previous partners) has seemed to amplify dramatically. As a base line, I have never had an issue with this when it pertained to celebrities or the likes, and I also have no issue with him watching/reading erotic content when we are/aren't together. It's just never been a big deal to me. Unfortunately, in the last month or so, I have found myself getting increasingly jealous and anxious about us due to him constantly bringing up "more attainable" folks and how attractive he finds some of them. We are currently only able to see each other about once or twice a month in person for a couple days at a time, and it feels like even when we are together, he is always talking about how he saw someone he found attractive or how he made friends with some random dude he met at a store and how "really, REALLY nice this guy's ass is and, oh, you have a nice butt, too, don't worry." The last time we were able to spend some time together is definitely what increased a lot of my worries about everything, though. Like I mentioned above, he is still friends with many of his exes. I have met a few of them and generally think they are all nice, cool people. Because he is still friends with a lot of them, we will occasionally talk about his relationships and even some of the intimate aspects (things he got to try, wanted to try and couldn't. Stuff like that.), because again, just never really bothered me before now. This last visit, though, he got onto a kick about one of them and blabbered for about an hour about how good the sex was, how it was some of the best he ever had, and how he still found this individual attractive but that I didn't have to worry because they never would have worked. That was a fairly big ouch for me.

I have brought this up to him on one occasion and, honestly, maybe danced around it a little more than I should have. His previous relationship ended because his partner was extremely jealous/controlling (he is not friends with this one) and that has been blaring in my mind any time I think to discuss it with him a little more firmly. I love this man with all my heart, and I know he genuinely loves me, too, but I am concerned about what kind of tiff a discussion like this would cause. Even just hypothetically. I am not entirely sure where to even begin with it, either. When I talked about it with him previously, I definitely did it in a more joking/soft way because I was worried about upsetting him and it essentially boiled down to me telling him he probably shouldn't look at other people's butts so much if I'm right there. Clearly, not the most effective take, as he still brings things like that up. We've had discussions in the past about cheating, as well, and my stances on it. I would bet nearly everything that he would not even consider it, but there's an ugly, nagging part of my brain that insists on it being a possibility. I do recognize that my stress about our relationship has also increased dramatically since we are now long distance and do think that may be playing a big role in it. On the same, self-aware hand, I also feel like I have dug myself a bit of a hole by being so unbothered about it until this point. I definitely feel I am being paranoid about everything, but also, genuinely, feel like he is being rather inconsiderate of my feelings. When we are apart for weeks/nearly a month at a time, I do not feel like hearing about how sexy he found someone else.

For anyone else who has been in a ldr and struggled with similar issues, how did you approach it with your partner or ease into those conversations? And what sorts of conversations would you recommend having about this topic, so it doesn't end up popping up again down the line while we are still long distance?

Thank you and sorry the messy rambling!