You are a big girl / boy now.  But still not an adult ....

But with today's exposure to TV and the Internet, there is really not much you don't know.  But the question is not if you know it but can you handle it ?

To handle it, first understand it.  As you're growing up, physical changes will occur and it happens  to everybody so there's nothing wrong with you.   Along with your physical changes, you may also begin to undergo mental and emotional changes and there will be a need to develop socially as well.