What to expect

So I am 13 and my mom thought it would be a good idea for me to pay my first visit to the obgyn some time this year. I masturbate but have never tried anything internal, and I want to. If I go to the obgyn, will she know that I masturbate? Also, do they ask you that kind of stuff?? It's not exactly that I want to hide it from my mom, but I'm extremely unsure of how she would react.