Gender-Questioning/Advice?

I am nearly sixteen years old (In September). My parents are extremely 'southern' they don't talk about sex, and think it is impolite to discuss it, or anything related. However I have a different opinion than my parents. When I was around eleven I started masturbating. I didn't know what it was, or what I was doing or feeling. As I've gotten older, I've found out more, and began watching pornography. I've noticed in myself that I have a type of.... nub? In my vagina, it feels like a small circular body part, with a hole in the center. I am not sure how to bring this up to my parents without them being angry about the fact that I masturbate. I am also adopted, so I am not sure wether or not what I'm experiencing is genetic or not. Also I have looked it up, I've googled it, looked it up in libraries. I don't know what is happening. Any advice given on telling my parents, or on my other... 'Condition' will be much appriciated.