I love my best friend...but

I know it's a total cliché to fall in love with your best friend, but I have. He's the only guy I've ever felt this way about. Yeah he's younger and all my friends think I'm a cougar for liking him, but he's perfect to me. We hang out a lot and sometimes it feels like we are dating, but I have to remind myself that we aren't. He knows I liked him a couple months ago, but he doesn't know how I really feel anymore. I don't know what to do. Does anybody have advice for me??