Afraid to tell my bestfriend I love him. Help!!

Portia
I have a guy bestfriend who has been my bestfriend since 5th grade and now we're finishing up college. Well I am, he's done. But any who he's always been in love with me. I know that for sure and I know that I've always loved him and we've tried to do the relationship thing back in high school but I was afraid to move forward with it because I was afraid it could ruin our awesome friendship but now I'm feeling like it's now or never to tell him that I truly LOVE him and want to spend the rest of my life with him but I'm still afraid and don't know how to tell him and he's thinking about moving away soon . Help!! How do I tell him??