Does he like me?what should i do?

so i've known this guy for like 3 years. he says he hates me but we are like brother sister bffs. when we are at his has in the pool he'll throw me in and carry me around and stuff. everyone says were gona be going to prom togeather and even his stepmom thinks he likes me but i don't know. we hang out at the mall and movies all the time. he flirts with me non stop. we even just hang out in my room and eat popcorn togeather. i don't know how to ask him if he likes or tell him how i feel. do you think he likes me and how should i find out if he likes me and tell him how i feel?