Ask him why he did it. He did tell you the truth and he's making an effort to get you back. I think you should talk to him, ask him why he did it. Think about whether you can trust the guy after this. If you can't no matter what he says, leave him. You may love him, but a relationship is nothing without trust. Im sure you know that. If you do trust him still and he tells you why, if its something you can both work on, then dont break up
just talk to him...
Maybe ask him about it?
& if he is, break up with him..
just talk to him...