I can't stop thinking about my best friend, what should I do?

My best friend who is a girl is all I think about. I can't get her out of my mind, were close and I can tell her anything. I dream about her, I fantasize about her, giving her massages and having romantic interludes with her(lol, it's true). I wanna tell her and I love being with her, being with her is like a natural high, she's so intriguing. What should I do?!