Help Me Understand

So I'm 15 weeks pregnant with baby number three. I have a boy, and a girl already. I would LOVE another boy, and since this is our last baby, I'm having a hard time coming to terms that, if it is a girl, that's it. I feel like shit saying that, because obviously a healthy baby is all I really want, but I feel like I'll be a little disappointed if it's a girl, and I don't even know yet! If it is a boy, I have no problem closing up shop and saying no more babies. Help me understand why I feel like this, and it's okay to feel like this.