I'd actually just suggest at least a few sessions of couples therapy, where you can determine if the two of you want to still be in a relationship, whether its the form it is now, or maybe you two step back from a marriage sort of dynamic date each other but also date others. A poly friendly therapist can also help ask the questions you both might be missing about if poly is a realistic or viable option for the two of you.
I sure wouldn't want to be the girlfriend of a couple who had such obvious issues still, and most people wouldn't. Mainly its the fact that you are hung up on how "she did worse" than you did makes it seem pretty clear that you two need to work through that problem before inviting other people to get entangled with you.
Happiness will never come to those who fail to appreciate what they already have.