From my experience, emails help, brief ones saying that you are thinking about him, don't make them heavy or full of thought or feelings -- that will cause some stress. Just a short sentence or two. Phone calls will come when he makes a sign. Just let him know how you feel, but "don't lay down and die for him" so to speak.
He doesn't want you to know how he feels just yet. Something has triggered and he is going to feel like working it out on his own. He is going through a time of believing he can't love properly like you deserve. He is going through a self destructive phase and in time he will realise what he has done. He'll have to hit rock bottom though first, he probably sub-consciously knows this and doesn't want you aropund to witness it. I waited two years for my love (who suffers from PSTD) to realise who can help him see the way, that he doesn't have to do it alone. And now a year later, we are only beginning to scratch the surface of what happens when someone with PTSD starts to realise they are not completely crazy, just a little unwell as the song goes. There may be areas of your life you need to strengthen and protect yourself. Use this time, and you will work out your own way. It's painful letting go, but it's for the best, you can't control him, you'll never fix it for him, the best thing you can do for him and yourself is become emotionally fit and well. Don't pity him when he gets back in contact, just support him and be honest. You heed to let him understand how his actions affect you and those around him who love him. But note i said "let him" understand, don't try and make him understand, just allow him the space, respect and honesty to work it out himself.