Fwb??

Okay so guess who came crawling back... my ex! And I never got over him we broke up for 4 months but he's coming back asking to be fwb (friends with benefits) . Let me explain, so I don't know if you guys know that Sarahah app, it's to post anonymously to other people, so I sent it out to some people on Snapchat and I got a few and asked my ex if he did one, he said he did so I guessed. He said "honestly I'd still clap" or something fuck boi ish like that. I just responded sarcastically, then we actually got deep into conversation about having sex again. So today we actually were supposed to make out but that didn't end up happening. Tonight I set some rules, I told him, If this did happen I don't want you fuckin with other people, I don't want to be "one of them" I also told him everyone knows him, the rumors could get out and I'd be labeled something I don't want to be labeled. I told him he can't talk about it with people because I don't want to ruin my face. He agreed with all of that and now I'm here, I'm still not over him, in the last 4 months I've tried to get over him with other guys, it doesn't work... and now I'm debating, this is either gonna be the biggest mistake or best decision. What do you think I should do?