I couldn't do baby talk or sound affectionate. I felt silly talking like that, but I could see how it engaged him, so I am learning it. Playing is difficult for me, too, but I'm learning. Having an expressive face nurtures the baby emotionally. I associate my expressionless face with the emotional numbing from PTSD from my sexual abuse, but also from my mother not responding to me.
Facial expressions are very important to a baby.
Looking him in the eye when he nurses and bonding with him is important. It is emotional as well as physical feeding. I've learned babies need that. Being responsive empowers your child. My therapist also taught me not to leave him crying, which my mother did to us.