IDK What To Do

I ruined my marriage.... I fucked up so bad... I'm a cheater... IDK why I cheated. I fuck up when things get hard. That's how I've always been. My husband and I got into a stupid argument and he left to go calm down. I got mad at him for leaving so I called up this guy I had been talking to to come comfort me... One thing led to another.... And we had sex... My husband walked in on us in the living room. He just went upstairs, packed his stuff and left. I tried to apologize and begged him to come back but he's been ignoring me. He came back today to talk. I told him I was sorry and wanted him back and he said " If we are gonna fix this, I'm gonna sleep with someone". He said the only way he's gonna try to fix this with me is if I let him fuck someone. I know he's still mad and hurt. IDK what to do... I know I fucked up but I can't imagine him sleeping with someone else ...

Update: Okay so he came over again to tell me he doesn't actually want to sleep with anyone else. He just said that because he was pissed at me. He said truth be told he just wants to forgive me and let it go but it will take time for him to figure out if he can...