I have a friend I know or think I'm falling in love with. We always talk and tell each other everything. What do I do?

by the way he in a relationship but he is not really happy at the time and he always say he thankful for having me as a best friend and glad that I'm the only friend that understands me and this guy has been through hell and back and we have sticked to each others side and been there. Always call one another when we need to talk. Nobody understands how I feel about thus kid I want him to stay my best friend but my feelings are not letting me do that I feel like I'm on the edge and I need to say something but don't how and how not to make our friendship awkward for us both Please help me!!!!😩😫😭😥😰😨😰 My head is cold and so is my body

Wait for little while and pay attention to his actions around you. If he seems extra polite or nice to you, he might just like you. If it seems like he does, go for it!