Confused about my ex boyfriend behaviour could u help explain?

He's regretting that he didn't make the most of being with you. He might not be happy in his current relationship, and looking to get back with you just as a sense of security. If your happy in your current relationship, then tell him that. The fact that he's writing things on your wall which everyone can see just indicates that he is not thinking of you, and how his actions may affect you. Obviously the final decision is up to you, but i wouldn't advise getting back together with him. Hope this helps. And good luck.