Love distance love

Hi
Last year I met a guy randomly - we chatted for ages, exchanged e-mail addresses and kept in touch once every few days on a platonic basis via e-mail. I broke up with my boyfriend a few months ago (completely unrelated), then this guy I met (let's call him Dave), came to stay with me for a week - he's from a different country to me. We had a great week, during which he told me he'd liked me a lot when he met me, that he liked me now, and he raised the idea of an exclusive long-distance relationship. He went back to his country and we agreed that I'd go and visit him.

Then in the couple of weeks before my visit, he got another placement overseas on the other side of the world. I went out last week to visit him, and everything seemed ok to start with then he started being distant and quiet. I tried to get him to talk about it; eventually we did and we agreed that a long-distance relationship wasn't a good idea now because he'd be too far away - he claimed he hadn't known what to do, that he'd just gradually become aware that the reality would be too hard, and he hadn't meant to be distant for the days before. We had a nice few hours before I went where he talked about how it wasn't the end of things, saying I should come and visit him for a week or two in his new place, maybe he'd be in a different place in a year, etc.

I got back on Sunday. He called that night and we only spoke for 20mins (then he said he had to go), and since then he's only sent a couple of short messages - the first saying he missed me and promised to write more later (which he didn't), and the second of which was just chatty. He's moving overseas next week so he's probably busy, but he's never been this un-talkative via e-mail before. I didn't think he was deceptive / lying about everything... but now I'm starting to wonder if he just said lots of nice things to make it easier, and I don't know if he's maybe just not interested in me any more. It seems like a really sudden change of heart if so when he was so positive about everything three weeks ago and at the start of last week, but I can't think of why he'd not be in touch more after everything, when we'd agreed to be close friends, etc. Am I being paranoid (it has only been four days since I left!)? Or is it clear that he just doesn't like me any more? Is there any chance he just doesn't know how to act? It's not that I think anything could happen soon, but I'm just really confused and sad that he seems to have dumped everything so quickly. Please help!