Having a child is such a huge leap into the unknown, it's what makes it so exciting but also a bit scary. Maybe your fixation with having a girl is about wanting to be certain and feel safe about what lies ahead? To feel some sort of control?
Our children surprise us constantly in who they are and the choices they make as they grow. Boy or girl we can't know who this person will be.
Gender a case in point, I have known a few people who did not identify as their birth gender, they live as another gender now. Their parents likely never envisaged that, but it was part of their path.
It really is a step into the unknown but there are some truly wonderful discoveries along the way.
Congratulations btw!