I dont know what to do?

i am stuck im 17 and thinking im leading this guy on which i no is really bad but anyway i have never liked him before n his liked me for 5 year but i think i now fancy him so i need to know is it posible i could fancy him after all this time and im scared that i might b making my self like him i no it makes no sence but i mean i might be changing my oppinion also i really enjoy talking to him but im really stuck as i dont know whether i like him or not his my brothers friend as well also we talk alot and he is basicly saying he finks im really nice n stuff so i dont know if his making me change my mind plz help sooo confused