trying for third baby?!?

Ashley
I have 2 boys, ones 5 years old and 7 weeks old. My husband is all willing to have a third baby but he thinks I'm on the nuvaring. I wanna keep it a secret until I get pregnant and try to keep it from him until I go in to find out what we are gonna have. What are the chances of hiding my pregnancy for 5 months? 
What are the chances of having a girl if most of his family is boys?