I feel like a coward..

So I’ve known this guy since I was 13 and a half. I am now 17 and a half. They say that love at first sight doesn’t exist and that you don’t know what love is until your adult. Hes been through several girlfriends. And recently this girl Kasey was with him and he almost married her except he recently found out she cheated on him 3 times. His name is Robbie. I didn’t know before but I know now for a fact since I’ve now been through the relationship loop a few times that he does in fact hold an interest for me and he has for a very long time. It feels as if it’s finally my chance to be with him and I have no idea what to do. There’s so much more about the time I’ve known him I probably should say but I really don’t know how I should approach this situation. This is different then any other romantic situation I’ve ever been in because I love him. I always have and always will.