Discovered a Year-Long Affair...💔

Hello ladies. I don’t know where to even begin. I suppose I’ll preface with, my boyfriend and I don’t snoop through each other’s phones. We just don’t. We respect privacy, but have also agreed that we should never hide anything on them.

Well, I’m having trouble sleeping tonight, and his phone was laying on his pillow next to him. It went off and lit up, and I glanced, and saw a message from a girl I know as his ex. My curiosity got the better of me, so I opened and unlocked his phone and found a message thread with this girl going all the way back to January (We started dating July ‘17, this thread starts January ‘18).....of them talking about how much they still love each other, how beautiful he thinks she is, how much he misses their relationship, how much he wishes he could go back in time and change things.. there’s intimate photos exchanged, gps and addresses of meetup locations, talk about their escapades....I am in tears and absolutely heartbroken 💔💔

What do I do? I have NEVER gotten the “vibe” from my boyfriend that he has been unfaithful. Ever. He always seems like he loves me so much, he always goes out of his way for me and has been a very stand up partner.....I don’t even know what to do. I have never even considered speaking to another man this way while I’ve been with him, let alone actually do all these things and still sleep at night next to him.

Please. I need encouraging words and advice on how to move forward. Feeling very lost right now.