Need a guys advise (whats he thinking??)?

ok ive known this guy for two years and he really likes me and my friends kept on going hurry up ask him out you can tell he wants you and i liked him too so i asked him out and he went bright red and said no and it was really weird cause he was like flirting with me and stuff for ages and now he wont talk to me and is avoiding me i dont lke him any more because hez acting weird but seriously why???