I'm getting mixed signs, what do I do?

This guy in my grade named Jaden has been my Mathletes rival since forever. But Jaden says he "hates" me and I decided that if he hates me, then I hate him back. He says that he has a crush on my best friend Milly, but we started talking to each other again by Facebook and texting, sometimes we fight but still. He says that we still hate each other, but everytime I spend time with him, I see me falling in love with him just a little more everytime. I sometime see him flirting with me and teasing me. But I don't want to hurt my best friend and she says it okay with her. Does he like me or not? I'm confused.