I NEED HELP

so I'm gonna be hanging out with my bff tomorrow for Valentine's Day. The only problem is I THINK I LIKE...LIKE LIKE HIM. I'm almost totally sure of it now, and I wanna tell him, but idk how. I've been thinking of writing him a letter, but I can't find the right words to say to describe my feelings. Also I can't write anything without it sounding cringe or lame. Then I thought about writing a song, but I know nothing about making music (i did find it's easier to put my feelings into lyrics though). I'm too nervous to say it out loud, because what if he rejects me and people overhear and everyone laughs at me??? Also how would that even go?? How do you casually tell someone that you love them?? Maybe I'm just overthinking all of this, but I'm so lost. I've never felt this way before.