How can I help my codependent ex boyfriend?

Hi there,

My codependent ex boyfriend broke up with me a while ago when he met someone else, who is manipulative and controlling. She convinced him to break up with me, and now has him believing that *I* am the manipulative, abusive, toxic, etc. one; and that our entire relationship was fake, and just a sick game for me. While this is obviously not true, I mean, very obviously - anyone can tell how much I care about him within 5 seconds - he seems to really believe it and has blocked my phone number, and won't respond if I use another number. He doesn't even sound or act like himself anymore; it's scary.

I have been to his new apartment once, and though I wasn't paying much attention, I remember roughly where it is and could easily find it.

If I do go over to his place, the problem is, what do I do? What should I say? I am terrified that he won't believe me, it breaks my heart that he doesn't think our relationship was real and I would be devastated if he remembers it that way forever. Also, his girlfriend could very well be there with him - and while I am not afraid of her, it would be much harder to convince him with her around.

Any advice on what I should do??