Welcome to the wonderful world of perpetual servitude. You won’t have gotten the orientation packet at the door, because you don’t read, not if you have any sense of self-preservation. It’s worth anybody’s life to teach you that, so don’t ask.
You will have been born into this.
However much your mother might have sheltered you from this—that is, if we let her keep you by her, and that might not have been a profitable decision, especially if she needed to go back to work in the fields after you were born—there will have been a moment when you realized what you were.
It may have happened as you were sleeping in the ashes with the rest of the children of your condition, in the charge of the dour old cook.