I like this guy way too much!

ok so I am 15 years old. I have liked this guy since I was about 10 1/2 years old. I like him a lot. I can never stop thinking about him and I get really jealous everytime one of my friends flirts with him or he goes places with my friends without me. my friends know how much I like him and they just cant understand it because they have never liked someone this long or this much. I think I still like him because I was never his girlfriend so I never feel like I got a chance… but I think he would say no if I asked him out even though we had a few times where I know he was feeling something. he would say no because his friends would make fun of him really bad and I know that isnt right but please dont answer me just to say what a jerk he is. I just need to know if I should try to stop liking him and if so how to go about not liking someone.