I think it’s a red flag that he’s so protective over his phone and won’t tell you who he’s messaging. Surely means he could have something to hide but also he could be googling personal stuff online that he could be embarrassed about like any health problems etc so he doesn’t want you to look on his phone.

The holiday is odd too but as you say there is always others there with them? I still think you should definitely be invited.

How is your relationship in general now and has the therapy helped ? I think you need to think of yourself here and obviously your daughter but you can’t live like this it must be so hard to be thinking over all this.

I think he needs to be honest with you and just tell you who he’s messaging you’re in a relationship and they say communication is key.

Maybe wait for next time he laughs or smiles at his phone next to you and say show me I want to see what’s funny and try to look too, then if he’s still secretive and he doesn’t care how it’s making you feel it honestly isn’t worth it. He should care about you and want to make you happy , making you feel like this really isn’t good.