Am I overreacting about my boyfriend and my best friend hanging out together?

For context, my boyfriend, my best friend, and I were friends before me and him started dating. She's been my best friend since we were in grade school, and then we met him in high school and are all in the same friend group.

I trust my boyfriend entirely and I know he'd never stab me in the back. And I trust my best friend too. But lately, they've been hanging out more when I'm not present. Things like, he's in a band, and she likes to go to the gigs all the time, even when I'm not going. Or they go to the gym together, not always just them alone, but sometimes it is just them. Most recently, he's been working on creating a brand and she's a graphic designer so obviously, I thought she'd be a good choice to help out with logo design and social media. But now they get on the phone a lot for business and today, they were going to his place to have a meeting. (it's a minor annoyance that these business meetings don't include me even though I thought I was part of it, but whatever)

They never try to hide these things from me. They've never been secretive. And they've never been caught doing anything malicious.

But I'm uncomfortable and I don't know why. Because I'm not worried about cheating, so why does this bother me? Am I just being possessive? Am I being stupid?

Other things to note: She is in a relationship, but it's rocky and they've been fighting a lot. When she's vented and asked for advice, she often references how my boyfriend does "x" so why can't hers do "x", or make comparisons like that? She's gone to us both as a collective for advice. But she's never expressed an actual interest in him, even before we were dating.

I'm just super uncomfortable now and I hate it.

Am I overreacting about my boyfriend and my best friend hanging out together?
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