He fucked up?

Okay, I posted a few days ago about my partner and I getting into an argument which resulted in him going for a walk to cool off. He left at 930pm and didn’t return until after 2am. Went to bed (I slept in another room) and I didn’t see him until 1pm the following day. Eventually he told me he went to a bar to watch the game and I had a gut feeling something was off.. his son picked up his phone so naturally I took it away to put up… I seen a random number, I decided I was going to look. It was a message that said angel. Nothing else. That night he took off he got a friend request at almost 1am, his phone was off or dead at that point. The request was from a girl, very pretty that worked at a bar nearby. He lied about what bar he went to, obviously met her at this new bar as we just moved. She ended up messaging last night, I responded casually and she responded again. The messages aren’t sexual but again, there’s only been 3 exchanged. I haven’t said anything to him but I responded on his account and he must of seen that by now… regardless. He met a girl, gave his social media and number. She’s now messaging him. Even if it’s not sexual.. it’s still fucked up he didn’t mention it. Like he lied about his whereabouts, took off for hours, failed to mention this lady friend but told me everything else he did. Like what do I do? Is he wrong? I feel betrayed. She’s gorgeous and single

I don’t know what to do or what to even say to him… how do I bring it up? I’m bad with wording things and getting out what’s in my head.