Guy's Behavior

Why is my crush suddenly ignoring me, and being weird around me?

so i'm 14 and i'm pretty sure this guy i like, likes me too. all his friends told me he does and i can kinda tell. i haven't told him that i like him though. were sorta friends. sometimes we walk home together but his friend usually comes so then we don't really get to talk that much. and thats the only way we can talk because we don't have any classes together. But we used to be really good friends! now he just kinda ignores me.
like today he was walking and i was behind him and my friend was sorta behind him. so then i waved to her and said Hi Olivia!!! then he looked back and just stared at me for 3 seconds and just started yelling and laughing with his friend.
PLUS! i already know he likes another girl cause his friend told me.
but I don't know if i did anything wrong or not.
it makes me really sad because i really like him and he's a really good friend!
please help me on why he's ignoring me!
:(
Why is my crush suddenly ignoring me, and being weird around me?
Post Opinion