Why is he acting like this???

The guy who i like remembers my name the next day after having lunch on the same table with him. He would ask questions about me, and everytime we see each other in hallways we would greet. But he'll notice me from afar and keep looking until an eye contact is established.. im not sure if it meant something.. but its almost like he wanted me to notice. he also added me in facebook. He have not talk to me in facebook yet... its been a few days now.. I wrote him a wall saying something like "O, you gave me the wrong direction to so and so thanks for the add haha" no reply still :( but then he replied me personally when we were in the school canteen. He even asked what subject i took the other day and we had a really nice conversation until my group of friends saw me and he said cya and went away. But recently he does not notice me as much anymore... why?? but i really like him and dont feel like moving on...