Really sorry if this is a bit of an essay but I would appreciate any opinions/advice.
For background, my partner and I are 27 and have been together for 2.5 years. We have known each other since we were about 16. He has been the most loving, supportive, faithful person since we got together. It is a wonderful relationship and we bring out the best in each other. Currently we don't live together but we have recently started looking to buy our first house.
Last night, I was watching a programme on our Ipad which is linked to his phone. At the time, he was on the train home from work. He and his friends were having a group conversation over imessage and every incoming message popped up at the top of the Ipad as I was watching iplayer. One text appeared referring to a girl as "the one that got away, hey MrGenie" and I couldn't help myself - I opened the group chat to see who they were talking about (please no lectures, I already feel terrible and have never felt a need to snoop before). I soon realised that my partner had sent to his friends an instagram picture of a girl in a dress with her chest out. My partner had commented that he didn't know what he would do if he saw her like that. Cue the most disgusting discussion between these men joking that she was asking to be raped wearing that, even a judge would agree, etc. Gang rape was also joked about. My partner was actively participating in this chat, talking about a time when he went home with this girl after a night out and had "finished" in the taxi before they even got home because she was so hot. They didn't end up sleeping together, which he said he was "still gutted about".
Needless to say I am devastated. Reading that conversation was like reading the messages of a stranger. I have never seen this vile side of him and I feel like I don't know him at all. To me, it is so out of character but maybe he is just an absolute arsehole when I am not around. I am disgusted by the things he said and disgusted by his friends. I feel disrespected, humiliated, terrified that I do not know my own boyfriend.
I have been at work today so have avoided seeing him, but we have an appointment with a mortgage adviser tonight so I am supposed to pick him up from work in an hour. Currently, I can't even bare the thought of looking at him.
Am I overreacting - is this something you could get over? I know that these texts were sick jokes but even joking about it crosses a line in my opinion. I am distraught at the thought of ending this relationship but he obviously has this revolting immature side of him that only comes out when he's with his laddy mates. I'm not sure how I would trust him when he goes out with these friends in the future, or how I would ever look his friends in the eye again.