So many step back for financial reasons and parents are a common stepping stone/path during a post divorce era. It's typically a safe place to land. Happens all the time.
I'd say continue creating your nest egg with work and the fewer bills that occur by virtue of staying with your parents. Keep working with your therapist to unravel the awful things that are replaying from your ex husband. Rebuild yourself -esteem and confidence.
It wasn't nice of him to run off and leave you for another woman. No it doesn't mean you are going to be like her?? Where did that idea come from?