My bf hooked up with my best friend

I had to come home from college for the weekend and while I was away my boyfriend hooked up with my closest friend and it really hurts.

This is an open relationship though but I feel kind of uneasy how it happened with my friend. Like if it were someone else I’d be fine, but...

They said they were just hanging out playing video games and then that shit happened. I mean we’ve all hung out together and I’ve kind of noticed that they were being “overly” friendly. They’re kinda my only two friends that I hang out with so I don’t want to lose them...

I feel like I’m being a petty little bitch but idk. Ik the sensible thing to do is to talk to him but I’m just not good at talking and I don’t want to be annoying and petty. What do I do??