You are allowed to change your mind and go back on your word that was given to a liar and cheat. At a time of vulnerability, he continued to be the POS that he is and put his false reputation above your authentic feelings, and tried to keep you reeled in. He was already doing it to you without your consent when cheating on you. He just played you like he has your consent now. No. It's not consent because you were too vulnerable to advocate for yourself at that time. But you know better now and you are stronger now and you can advocate better for yourself now. So that's what you should do. Tell your friends that he manipulated you to lie to save his face and that you were too vulnerable at that time, so you agreed. But you can't do it anymore. If that blows up your friend group, so be it. POS should have thought about that before betraying you. This is on him, not you. Better that a friend group based on lies and deception breaks up, than you breaking down from trying to keep the lie going. Be a good friend to yourself first.