WONDERING IF IM ALONE IN THIS

So my husband and I have been blessed with three beautiful girls. And I have a Step-son through my husband. I know we are blessed beyond belief, but I cannot help but to feel this desire for a son of my own. I love My son to bits. Wouldn't trade him for the world. But I have always wanted a baby boy. I've known since I was 9 years old that I wanted a son. And lately every time we drop of my son with his mom I have this cut wrenching feeling. We miss out on So much with my son due to the custody arrangement. I want to do so much with him. But I can't. I guess I just want to know if anyone else has expierienced this. Does it go away? Its been 4 months and my desire for a baby boy of my own only seems to be getting more intense.

Edit: to the people who pointed out the bonus baby thing. I fixed it. Y'all are right there is no way she will know. Thank you for the messages of support. 💖