Is this love or infatuation again?

First if she is a good mother to your son, be grateful. I'm a old man with many ex's, been exactly were you are right now. I can feel that your hurting but ask yourself, do really love her? If you do then let her go. Learn to be her friend and support her. Tell her your happy for her and mean it. If you can't do that, ask yourself does she belong to you? If say yes, than you don't love her. No one belongs to anyone else. She has a right to seek happiness.