How should I tell my BFF I like him?

My best friend and I are extremely close. I have had feelings for him for a while now, but I just let them slide and didnt think anything major about it…but a few weeks ago, we were out and holding hand and sitting with eachother all day, and that made the feelings come back stronger than ever. I now cant stop thinking about him! our friends, his brother, and even our parents(!) think that we are perfect for eachother and wonder why we arent dating. I need advice! my friends arent very good with relationship advice, and I dont know what to do! I most def want to tell him my feelings, but I am afraid of rejection, and that he might not feel the same way. I think he does, but hes not very open to talking about that stuff. we tell eachother almost everything, so why is it that I cant talk to him about this. I dont want to loose my best friend because of it. HELP! what should I do??? and how should I talk to him about it???!!! thank you soo much!