Plan b definitely. If you're only friend and want to be only friends,you shouldn't be having sex. I mean it's your life and your business but sex just complacates everything and your relationship as "just friends " is already more than "just friends" if you don't want anymore than that out of him stop what you're doing right now. Especially if he is having unprotected sex with you? Um, you need to be woman enough to just say no. It's your body make a stand.
Morning after or plan b pill. I believe both is effective 72hours after unprotected sex