Why don't you have a vaginal opening?
== == There is a thin membrane of skin, called the hymen, that
covers the vaginal opening in most girls before they have engaged
in sexual activity. The hymen will have some type of opening
through which menstrual fluid can pass; however, it could be
possible that this opening is so small that you would not notice
it. If you are concirned about this you should speak to your doctor
about it. Note that you do not have to tell you parents (and you
doctor will not tell you parents) if you talk to him/her about
sexual questions or problems.
Because you are a boy.