Why did he do this to me just WHY!!!!!!??

Ok it all started when he first started to flirt wit me by always sitting next 2 me, puttin his head on my shoulder, sitten on me for some reason, annoying me just 2 get me attention etc... But when he did all that I started to like him well who can resist a guy doing these things to u. Anyway so i started liking him and so i thought he liked me back so i told him. Was that wrong? Then he starts 2 ignore me and now i am really upset and pissed b/c what kind of guy gets u 2 like him then just blows u off i ean he used me like i dont even matter!!!!! It really pisses me off b/c i cant even ask him why he is doing this to me cause he runs away from me like a stupid cowardly dog. uuuhhh.....help there is a pool party coming up and we are both invited i dont want to have a crappy night!!!!! plzzzzz help me!!!!! Thx xoxoxo