I love my brother so much, but how can I quit my desire for him?

I’m a 13 year old girl and my brother is 17. He always looks after me and helps me with my homework. I find myself having this weird, sexual attraction to him. I didn’t want this to happen, but it just did. I’ve been having a crush on him for a long time. I saw him sometimes when he rubs himself in his room and heard him masturbate and porn incidentally. I can’t help but feel so infatuated with him and I even masturbated to the thought of him. I’ve never done this with a man before, not even in my dreams. I can’t help but feel a strong attraction to him. I’ve been doing this for over a month now and I can’t stop. I just really want to stop but I can’t. How can I deal with this?