Messages on boyfriends phone!

[TimesLikeThese]

Not new to mumsnet just name changed.

My boyfriend is out with friends and has left his phone at home. He phoned from a friends phone around a hour ago to tell me and ask me to check his WhatsApp for a message and send the details to his friend. It's arrangements for a weekend thing, that they are sorting tonight.

As I'm looking through his chats, I noticed my name mentioned in messages to two of his friends, along the lines of me, not knowing/him not telling me. So I clicked and read the messages.
Not proud of that and know I shouldn't have.

Anyway, on reading them it's obvious one of his friends has been seeing someone behind his DP's back. My bf and another friend know, although both seem annoyed with him about it.

Now my dilemma, I'm friends with the DP. They have 1 dc and she's pregnant with the 2nd. She's also mentioned to me that he's been off with her recently.
So what the hell do I do?
Tell my bf I know?
Tell her what I know?
Keep my mouth shut and try pretend I haven't see it?

My boyfriends relieved it's in the open. He was torn between loyalty to his friend (friends a long time too) and hating cheating and the effects it has on families, which he knows first hand.
He went for drinks with cheating friend and a few others last night and they have all given him a hard time over what he's done. He's apparently very regretful and all that and he's hoping she'll forgive him.
He's on the sofa at the friends at the moment, his parents know and have given him a telling off and said he's not welcome back there, even though they have spare rooms. I feel a little happy about that!

My friend text me back last night to say she's ok, obviously upset and angry and not knowing what to do. She's coming here tomorrow for lunch and a chat.

Wow what a situation. Glad it's all out in the open.

I have a similar tale from many many moons ago...I stumbled upon a married friend having an affair (I saw them, and she knew I'd seen). Her DH was my DH's friend, not close but mates all the same - we'd been hanging around as couples for years.

I never would have said a word - just on the basis that it was none of my business - but I did tell my DH. He is far less of a drip than me and said that if she hadn't told him within a month, he'd tell him himself.

It didn't happen that way in the end, but DH did manage to manipulate a situation where the friend's DH found out for himself (long story and outing).

It was horrific and friend's DH never forgave me for not relaying what I had seen. All parties are now divorced and happily remarried now, and friend and I are very close friends! Her ex-dh and I, not so much... But there we are.

you sounds lik a great friend and you did the right thing

I hope you had a nice lunch with her yesterday.
Well done OP.
You and your OH did exactly the right thing.