Why is my guy friend giving me a silent treatment?

I am in 10th grade now, and I knew this guy since 7th grade. I disliked him at first in junior high because he would try to annoy me, like making a gagging noise as he walks by me, or do that spiderman thing on me, etc. Eventually, we became friends in 9th grade. He became much less annoying on me since then. He even told me that I’m a really awesome person and told a group of guys that I am “like the prettiest girl at school.” Even one day, he wanted to ask me to go out with him, instead he wanted his friend to ask me out for him, but he got so scared he ran away. This year, we haven’t been talking that much but normally, when he always see me, he would say “hey (my name)!” And because I really do like him as a friend, I thought I would just go have fun with him by going behind his back while he was talking to his friends and poke his shoulder and then hide from him. He liked what I did at first, but then the third time, I did the same thing, he just looked at me and gave me a small hand wave only. That was last month, and since that time, he stopped talking to me. Now, he won’t talk to me or anything, and he just looked at me, he won’t even say just a hey or something. And I am known to be a REALLY quiet, sensitive person. I feel like he is my only guy friend whom I thought I could talk to, but since he has been giving me a silent treatment for the past three weeks, I feel really uncomfortable. I don’t know what is going on. Am I more likely to be annoying to him? Did I do something wrong? Or maybe he have that sudden thought of liking me that he started being afraid to talk to me? help!