I (19M) want to tell my best friend (19M) that I love him but I don't know how

Hi! I'll go by the name Astolfo snd we'll call my best friend Felix. So I really love Felix and have been loving him for approximately one year and I want go confess, but I don't know how.

I think I have a chance with him because he's bi and, well, the way he acts with me seems a little more than friendly?

Everytime he comes over we cuddle, kiss eachother's cheeks, tease eachother... I think we even kinda flirt sometimes? He also slept in my bed for like three days in a row and I'm inviting him over Sunday for a movie night.

I really really REALLY want to confess but I'm scared it will ruin our friendship or worse, that he'll mock me for even thinking I had a chance :(

Any advices?