bf troubles

so i was in an emotionally abusive relationship. but i confronted the guy and were working it out and that makes me really happy. but he made me depressed and made my life hell. i want to get back at him. i want to cheat on him bc he deserves it but i wanna spend the rest of our lives together. i just kinda want it to be even. and he'd never know about it. what should i do?!😩please keep in mind im not going to leave him so please don't say i should.