Lucy,
I think you should seriously consider breaking up with him, as he has cheated on you (cheating is emotional, not just physical) and is now manipulating you. He has no right whatsoever to be angry at you for finding those messages in his phone. If you’d found nothing, that is a different story. But he should be the one making things up to you in this situation, not gaslighting you into feeling you did something wrong. Please see the situation clearly. So many women fall into the trap of excusing toxic behavior in the name of saving a relationship. Then, when you’re 45-50 years old and the behavior has become worse, you’ll get a divorce and ask yourself why you wasted so much of your time. He cheated on you. He thought he could have an emotional side-piece, and got defensive when he was exposed. Still being angry at you is his way of manipulating you into staying with him by making you think you are guilty. The fact that he hides the contents of his phone is a huge red flag to begin with.
Wish you well. 🙂
Jane