My boyfriends ex sent me screenshots

So story time... me and my boyfriend have been together for about a year have known each other for over 5. He bought me a promise ring, he has introduced me to his daughter (whos seven) whom I’ve been her life for about 8 months now and absolutely adores me and I her. He Has absolutely no social media. Talks about having babies and shows me absolutely the purest form of love and respect. Says he can’t wait for me to be his wife. Has always given me his phone without hesitation if I need it for music,internet and other stuff. Today I received a fb message from a girl who I didn’t know turned out to be my boyfriends ex girlfriend (not the girl he has baby with) she sent me a screenshot of her and my boyfriend talking dirty and she has his number in it and everything so I know it was him. I’m not even sure if this is a question or a more of what the fuck should I do. He has never ever given me a reason to doubt him. Everything is always about me. The man adores me. I’m in so so so much shock I think I can’t breathe. He denied all of it said she’s mentally ill and has done things like this before. I’m so torn. Never for the rest of my life did I ever think I’d be posting this.