cheating

So I went thru my bfs phone on Friday and I saw texts of him with other girls on kik, snapchat, and IG. I'm obviously upset but when I told him about it all he could tell me was "why would you go through my phone" and he still hasnt apologized or anything and he's been talking to me like nothing has happened. But i can tell the way he texts isn't the same. I really love him but I have a feeling he won't change. But I just can't leave him.. I really can't 😞 idk what to do anymore