Is it normal to want so badly a guy you hardly see or talk to?

So I'm 17 and met this very good looking guy last year who's 20. I knew who he was before we met cause we had some friends in common and I often saw him when I went out. At the end of one party we were both a bit drunk and talked a bit, some weeks later I heard he talked about me to a friend, said he thinks I'm pretty, etc.
So in October we were at a big party and he came up to talk to me, smoothly sending signs that he wanted to hook up with me. To be honest I was really tempted, but firmly said no because I was together with another boy at the time who was at the party too.
Then on the next day he added me on FB and asked for my IM and we started talking for the next few weeks and I became really into him, but slowly we started talking less. In December we met again by chance and then finally kissed. But we continued to talk only every once in a while, he travelled, I travelled... Anyway, now I hardly talk to him and we have met only in bad situations that we cant be together again, but I think about him a lot... But I dont think he is as interested on me as he used to be :( Should I wait to meet him again and try to increase his interest, or should I just let go?