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You truly believe that it’s post partum depression? If so, I how do I say that to her without upsetting her. She is a very sensitive person.

It sounds like bad postpartum anxiety which can overlap with postpartum depression and sometimes progress to OCD or, rarely, psychosis. You might try speaking with her physician first - they cannot tell you things about her without her permission, but you CAN tell them what you're seeing and your concerns about it. You can also try gently mentioning to her that you think she may be experiencing some postpartum issues and perhaps she could speak to her doctor about it? Of course, telling women their hormones are off is dangerous ground for a man! Does she have a sister or mom that you could approach about this? Maybe coming from another woman she could hear it better? I have a good friend who had such bad postpartum anxiety that she never wanted to have another child. She was terrified she might accidentally hurt her child, or something awful might happen. I never knew the depths of her disordered thinking at that time until recently - this occurred 30 years ago.

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Second can you give me and example. How should I respond to say something like this?
“Dad I have always been afraid of you and I never wanted to be with you.”

I'm so sorry you felt that way. I love you with all my heart and I never wanted anything but your happiness and safety. "