Choke me out!!

My boyfriend and I were having some pretty kinky sex...he slapped me hard around the face, flipped me onto my front and told me he was going to fuck me like a dirty whore. He stuck his cock in my ass and loved how dominating it felt 😍 He put me in a head lock and started chocking me..he told me he was going to choke me out and fuck me while I was unconscious. It got close but I whimped out last minute....he's an MMA fighter so he knows how to do a blood choke properly and safely (well safe for a choke) but I've never been made to pass out before. I really want to because I find the idea of it hot af 🙄 anybody done it and want to share their experience or have any tips for how to stay calm?