I know you know the right things to do, and I know how far you've come -- a looooooong way :ghug3
In my own little world, the way that I got to where a reaction was "natural" to me was to practice, practice, practice. Meaning: if I wanted to be ready when my X called, I had to practice healthy behaviors over and over, until they felt natural, second-nature.
You're still holding out hope that his thing with the other woman doesn't work out, it sounds like? Is there a healthier set of thoughts you can think instead? Like "I will never be taken advantage of again." Or "THIS is the life I want my child to have, and I won't put him through any more pain." ?