I think blaming the OW is quite destructive. You're going to look at 'everything she has got going for her' and compare yourself unfavourably. That is not treating yourself in a dignified manner.
You have been treated dreadfully unfairly. It is absolutely awful, I know.
You deserved to be treated better and you were let down by two adults. One of whom swore to God (or the law) to not do that.
Your self-esteem is through the floor right now.
You need to start feeling better about yourself. Look at your fine qualities, start treating yourself to things that make you feel good. You deserve to be a happier person.
Also, you need to tell people what you are going through in real life. Like you, I made the mistake of hiding away. Once you start telling people, they start telling you things that they like about you. They offer you great support, help you feel valued and loved. Do yourself a favour, and don't fight your feelings alone.
Of course, some of them will want you to split from him. But if you decide to stay and work though it, then that's your decision to make. You will make the right decision for you.
Eventually, people will forgive him, but in the short term it will help him understand just how utterly disappointing he is. It will give you some much needed support. It'll stop you fighting your feelings alone.
And that, love, is how you will regain your sense of dignity in my opinion.