Why is it that the men we want rarely or never show interest in us?

I met a guy last month through a mutual friend and for the first few days that he was in town, it was very obvious that he liked me. When I visited him a few weeks ago, I still had that impression, but he wasn't as affectionate like when he was on my turf. He's moving to my state in a few months and I want things to work between us, but the calls, texts, IMs and FB emails have become so scarce. Is he losing interest? What should I do? How can I keep him interested