Update:
Well, he's gone (the new man) and I'm having a horrible time with anxiety and pain over it. Partly I miss him, partly I feel very insecure about whether he cares for me as much as he says he does. I told him to begin with that we didn't have to be exclusive, but now I feel horrible at the thought of him with others. I had a panic attack last night because I saw he 'liked' a photo of a girl from his home country. I know I don't want to live like this, I don't want a possessive jealous relationship, I want to just be able to enjoy someone's company and be ok with not knowing the future, and with something more complex than 'black and white' thinking. but i feel i can't help myself. Perhaps the fact he is so laid back makes me worry for the both of us. And the fact he's not unhealthily obsessed with me makes me insecure.
As for the ex, he's sent me a letter, and a text and re-added me on facebook. he's just said one or two 'friend-like' things, told me he's doing great and apologised for how he took the breakup. I think it will be ok. At the moment I know I won't go back. But I'm worried for the future. I feel so empty without the new man to fill the void.