When Should My Son Meet His Father's New Girlfriend?

So I need help with this. So my sons father told me last night that he has a girlfriend now. When do you guys feel it's an appropriate time for her to meet my son? Obviously I'm meeting her first. And also he told me that the one weekend that he didn't respond to me was because he was talking to her. Him and I are in constant communication. That bothered me because our son is more important. I send him pictures every single day. I text him and tell him about what's going on in our sons life. I expect him to respond. Don't get me wrong I'm so happy for him and I'm the one who encouraged him to get out there and date. My only concern is that he will let it get in the way of him and his son. How do I tell him how I feel without coming across as some crazy baby mama?