My(27f) partner(30m) is being a bit too close to 20f coworker and idk how to address it

My(27f) partner(30m) is being a bit too close to 20f coworker and idk how to address it

My partner has been speaking to his coworker a hell of a lot recently, it started after he helped her with a bullying situation at work which was obviously okay.

My problem now is that over the last few months every morning I wake up to the sound of his phone pinging and it’s always her, every personal situation she’s in she runs to him for help and advice, from what I’ve seen he hasn’t hid anything from me and messages her in front of me, I know almost for certain nothing has gone on physically however I’m starting to feel uncomfortable with the closeness. A few weeks ago I asked if he wanted to watch a certain show and his response was “no that’s mine and X’s show” (their job allows for a lot of spare time particularly on nights) it feels like he’s become her emotional crutch and I’m afraid to say anything because as of recently he’s started to feel a lot happier in day to day and doing more on his time off and spending time with our friends I don’t want him to withdraw if I say
“this is making me feel uncomfortable”

How should I go about addressing this situation without feeling too accusatory?

TL;DR
partner is being a bit too close to a coworker and I’m unsure how to address it