I keep going in circles trying to deal with this.

TLDR: I’m insecure lately about how close my bf and his female best friend are, even though nothing they’re doing stands out significantly as wrong. Talking to him doesn’t seem to help overall, I’m going to try talking to her. How can I address this with myself and with her?

My bf “H” is very close friends with someone “N” that he dated briefly in high school and had a stint as fwb with early in college. They decided pretty quickly that they enjoyed spending time together and understood each other well, but didn’t solve problems together well. They think really similarly, for better and for worse. The romantic/physical connection never went away fully, but they decided originally and again with the fwb situation that they just do better as friends.

A couple years after that I met him and we’ve been together 5yrs, and he’s stayed friends with her with no issues. Lately though, since they have similar work schedules and I have an opposite work schedule, they often see each other more often than I see him. It’s not intentional, it’s just not possible for me to see him more.

I’ve been more insecure the past year of so of them being so close. I’m not sure what to attribute it to, as his friendship with her is not really different in any discernible way from his friendship with his male best friend. I’m not so anxious when he spends any time with other women, just her. I’m not actively afraid he’s cheating on me or is interested in doing so. He and I toyed with doing an open relationship and talked about if she would be an option for him. He didn’t push, but I agreed bcs I was anxious already but that thought didn’t make it any worse. She ended up not wanting to anyway, but my original anxiety is still there.

Only additional context is that she’s not my biggest fan, and is nice in person but we’re both kind of reserved/awkward. He talks to her about our relationship, good and bad, but she doesn’t seem to feel like the good outweighs the bad that we’ve gotten through.

I know as much as I do bcs he’s very open with me about everything they talk about and how he feels. There’s nothing specifically going on that’s wrong, so why do I feel like this? What can I do about it?

I’m going out with her next weekend to talk about it and clear the air, but I’m not sure how to go about it exactly. How can I fix this? Why am I feeling like this? What can I do about it?