My friend

Short and simple, I have a crush on my best friend (he's straight), he doesnt know im gay. Should I tell him I have feeling for him at the risk to lose him. Or I dont tell him and I will feel like shit for a while, a long while... Should I tell him or not? I really dont want to lose him (even as a friend, but I also want to feel better, which I cant unless I get the feeling off me.