TLDR at the bottom

Please bear with me as this is really raw as I just discovered my anxiety about this situation was apparently warranted.

My fiancé (C) told me he was going to meet with an old friend and have dinner with them this past Thursday night. Which I’m totally fine with, he doesn’t go out often so it didn’t bother me. What DID bother me, was that he gave no context to this friend (i.e. gender, if it was an ex, what they would be doing other than dinner). He barely messaged me through the time he was out, which again didn’t bother me. But he didn’t tell me anything about it when he got home. At 3am. Didn’t tell me anything about it the next day, other than saying he showed her his new truck and its features. I guess he didn’t realize that he never told me the fact that it was a she, bc he immediately followed up with “I saw the face you made, nothing happened” and promptly changed the subject. I didn’t bring it back up.

Cut to today, my anxiety got the better of me and I ended up going through his phone (which I have never had a desire to do, despite us each having free access to each others phones). In the conversation with his friend, I found some sexual/sex hinting messages, when I have told him before with other female friends that I don’t like him talking like that with anyone other than me. He doesn’t know that I know this, considering it just happened and he’s asleep. Yes, I feel shitty going through his phone while he’s asleep. But our wedding is in two weeks, I couldn’t let the anxiety fester and not say anything about it.

The advice I’m looking for is just… how to go about bringing up this conversation that I know needs to happen. He needs to know that I went through his phone and what I saw, and I need to know why. Does anyone have just words of encouragement or advice on how to start that? I’m happy to answer any questions anyone has. I just need help and my normal advice friend isn’t answering me 🥹

TLDR; my fiancé met with an “old friend” last week and didn’t tell me anything about it, I found texts between them that make me uncomfortable and I don’t know when or how to confront him.