Starting a LDR

I like this guy I met a couple of years ago, on an exchange trip to Germany (we both live in England and are 17). I told him I liked him, and we've met up a couple of times since then, once with mutual friends and once on our own (although it wasn't planned). So I spent a few days at his house, and he introduced me to his friends, and put his arm around me during a film, which I took to be a good sign (I have no previous experience of relationships and neither does he). However, since then he hasnt been very forthcoming. What should I do to encourage him, without scaring him off? (He's shy, nerdy, uses humour to deflect serious conversations and is 17 years old, same as me). Please help, because I don't know what to do!

As he lives about 3-4 hrs away, and neither of us can drive, I see him very infrequently, but try to keep in touch via text. The reason I am worried is that since I stayed at his house, where he was very attentive, his texts have been sporadic.