Am I Crazy Or What????????????????????Please help me out...........................…

i m just 15 years old .I started likeing a guy. He lives in my street and i use to watch him all the time when he is outside and he is 5 years elder to me but i never cared.i started talking to him as a friend and then i came to know, he already haves a girl friend..but still i use to think about him all the time like every single second he is on my mind.i know he haves a gf already haves but i never cared i still like him like crazy . i can't stay a day without talking to him.i can stay outside late night just to see him once in 24 hours .i tried so much to forget him but i can't .i just want him like crazy.the way he talks shows he likes me too but he is not saying anything to me..what do i do?i know he likes me.I don't know what to do.I love him so much and i can't help myself,i can't stop myself from loving him..........................