There is nothing wrong with you. It isn't easy to just pick up and leave any situation, esp one with children involved. Beyond his drinking and those issues, he is also very disrespectful. Bringing another woman into YOUR home and telling your child about it is a really despicable thing to do. It shows that there is so much wrong with him, not you.
I think when we stay in these kinds of situations, it is because we don't feel we are worth being treated better or that this is what love is like. You do deserve to be treated better and this isn't love.
You may feel 'stuck' right now because the shock of his behaviors is almost unreal. Picking up and leaving isn't always that simple but having a plan for your future is something you can think about. Then you will feel like you are doing something about it and when the time comes, you will take whatever action you need to.
Hang in there. You are being put through a lot and deserve so much better.