Why does he act so disinterested?

There's a guy who constantly stared at me and smiled for some months last year. Then he started ignoring me and one day I approached him and he was very nervous. I approached him a couple more times in June but still he wasn't relaxed around me. Untill September we haven't seen each other.

In the beginning of this school year he tried to get my attention by walking past me more often. Then he ignored me again. One day his friend asked me to approach him one more time. I did and he smiled a lot. Next thing I saw him in a classroom and he waved at me. One time he and his friend approached me when I was sitting on a bench. His friend did all the talking and the guy was standing behind me so I couldn't look at him. Once I saw him taking pictures of me.

Last week we added each other on Facebook and he poked me. My friend texted him saying I like him. He responded "really me.. but there are many other good looking guys xD" (he meant why have I chosen him particularly). He even complained that I'm constantly poking him instead of texting. So I texted him and it went pretty bad. He didn't want to admit he poked me first (he did admit it later) and then he just straight up asked me why do I stare at him. Again he didn't want to admit he started the staring (he did 100%). Then he left the chat for 20min without saying anything. He came back, we talked a bit but he seemed disinterested so I got angry and stopped texting him.

He knows I like him...so why is he acting so disinterested and rude to me ?