BF. Girls at work.

Okay I know this might sound "crazy" of me like most bitches would say but, my boyfriend has mentioned this girl at work he talks to who's been in a relationship for like 3 years and recently I saw where they were messaging on Facebook, I happened to have read some of the messages because I couldn't help it. But they weren't from what I could tell, flirting. But he gave her his number and I've noticed he's been looking her up a few times here recently. I've also noticed that her Facebook doesn't show her relationship status anymore. I know I might just be over reacting but I really dont like when a girl tries to befriend my boyfriend and doesn't even acknowledge me at all. We've also been together for 3 years and it's just all weird to me and I'm not sure what to do about it. It just gives me an odd feeling. Help. 😭 if I ask him about it he'll know I was creeping and he'll get pissed.