He's a cheater and imho hes the worse type of cheater, because
A. He'd probably never be satisfied with sex with only one person.
B. He has sex with multiple people, who themselves have e sex with multiple people ... Who themselves have sex with multiple people....and on and on.
He's subjected you to dozens potentially hundreds of people's Stds. Swingers go to local meets, regional meets, london/large city meets, clubs in holiday resorts, one on one meets if they can get them, there's even a camping/caravanning swinging scene. They cross over to dogging, the men often cross over to prostitution because there's such an imbalance in male Vs female swingers.
That's one big std factory. Condoms don't fully protect against eg HPV and herpes. Any intimate contact can spread those. And what if they break or come off.
You'd not realistically be able to relax and have unprotected sex with him again, even if you use condoms he's still a risk.
If you wanted to have more kids, youd be risking STDs during pregnancy which can lead to miscarriage and fetal abnormalities.
But why would you want to ... He's a scummy skeezy cheater and liar. He's not who he said he was. He's shit partner material ... And that's all on him.
If wouldn't be your failure to end the relationship with him, it would've your success.