How can i tell him how i feel?

im 15 in 3 weeks and since the age of 11 when i met this guy iv liked him and i was quite shy then so never said anything but i though with time my feeling towards him might go but the longer iv waited the more i liked him. and i think im starting to really love him (i don't care what some of you think if you think im too young to know what love is i just cont care i know it is when im with him nothing else matters its like nothing else exists just the two of us and it feels right like that's how its supposed to be). we start back at school on wednesday and really want to tell him how i feel about him but whenever iv tried to before iv never been able to say it aloud to him. its just getting too hard to stay quiet now no matter how much i want him to know. im going to be alone with him in music 5th period on wednesday and i wanted to tell him then. iv heard somethings from our friends that he likes someone else but the person he likes already has a boyfriend and iv been getting really close to him this last year. does anyone know any easy ways that i can tell him without ruining our friendship if he doesn't like me the same way because id rather be just friends then nothing.