What does he want me to do? guesses? important!?

So I am friends with this guy Clayton. He and I were just acquaintances first but I was always attracted to him. It was nothing serious though, Since he is quite reserved I did not try to approach him. I did not see anything happening between us. However, for the past few weeks he started giving me a lot of attention. He practically closed the distance I had created between us and tore down my barriers to be friends with me. But as soon as I started to respond as a friend he pulled back. Now I am even more attracted to him and have started to fall for him as i got to know him better. But he is pulling back into being very reserved. He is not making the extra effort he was making to be friends with me anymore. He is almost avoiding me. I do not know what to make of it. Any guess?