WOW! That is messed up. That is seriously messed up. If she is having it all at home - she is having some whorishness in her, I guarantee it.
You've got to think hard and think about ending it as supposed to continue.
Kid of 5 y/old is a huge responsibility. Have you read my link?
I am so sorry for this happened to you, it is going to be a hard road in nowhere (most likely). Please, think and strength to you.