Your self-esteem sounds like it's in the crapper. You might want to consider some individual counseling. There isn't any reason to compare yourself to anyone. If you are comfortable with who you are and the changes you are hopefully making for the better, then he's the one that is missing out. Who cares about this OW? She isn't fit to shine your shoes, regardless of whether she is a rocket scientist, brain surgeon, and supermodel all rolled up into one person. Keep this in mind....many men that walk away choose someone they see as beneath them. If he wants someone to boost his ego, then he's not even man enough for you.
In the end, it's not the years in your life that count. It's the life in your years. Abraham Lincoln
It is hard to fail, but it is worse never to have tried to succeed. Theodore Roosevelt
