I Have a Crush On Someone I Shouldn't

I like my best friend. And I don't mean I see him like a brother more like a boyfriend but the thing is we've been friends for 6 years now(we met when I was 12 & he was 17) AND there's also the fact that I told him I liked him 4 years ago and he told me I was like a sister to him 😖 He's the flirty type of guy and he gets touchy touchy with all of his female friends but overall he's a great guy. I want to tell him how I feel but I'm scared . I don't know if I should or to wait.