I've known lots of children with messed up things like this, but I fear it's not that it's really normal, as in how it would be in healthy kids, just common for children to have been abused. Maybe you should try to find a therapist with a great background in sexual abuse? They could help you sort out the truth at least, and if it is indeed sexual abuse, I'm certainly not qualified to really say, they would be the right person to see.