So confused about feelings towards a girl??

This girl's like one of my best friends, we're really close. Some days I just feel like that's all she is, a friend, and that's all I want her to be. But then other days I'll wake up and feel like I'm in love with her, that I just want to be around her and hold her a kiss her (one time I just managed to stop myself going in for a kiss). No clue what to do because most the time I genuinely just think of her as a friend and I'm almost certain she always thinks of me as a friend?