Me and my boyfriend have been together for a while. we were happy. a few weeks ago I got a message from someone I new from high school I hadn't talked to her since she graduated. she sent me a screenshot of my boyfriend texting her and telling her to come over and to cuddle. I confronted him and he made up this story about how he got drunk at a party once and some dude had his Instagram. I trusted him and I believed him. after that I started paying close attention. There were a lot of read flags. today my best friend pulled me out to talk to me while we were in class. she told me my boyfriend had messaged her and was flirting with her. I texted him and he got extremely defensive. then he started saying that if people are gonna continue spreading rumors then he doesn't want to be in a relationship. it was a huge red flag. she tried showing me the messages but he had unsent everything he had said. she told me he wanted to snapchat her. he kept telling her to show private areas. she wouldn't do it. after class she got a message from him saying "why'd you tell Emily I cheated". just a few minutes ago he called me and said that she started the conversation he denied having her snap and then told me that he blocked her and everything. he got pissed at me for asking again and he ended the call. the only problem is that since he unsent the messages I have no actual proof. I know that if I end it he's gonna start telling everyone that I'm the one that cheated when I didn't. I need help on figuring out what to do. how can I test him? how could I get hard evidence proof?