LGBT: i'm in love with my best friend... advice?

I've known her for three years, and I'm head over heels for her. She's not a very open person, so I'm afraid she doesn't feel the same. But the thing is, on my birthday she kept asking what I wanted. of course I replied with "nothing!!!' xD. But then she leaned over and kissed me. Then asked me if that's that I wanted. long story short, my heart went crazy. She knows how I feel about her, but she hasn't said ANYTHING about how she feels. I'm afraid it'll be too late if I wait too long. HELPPPP.