Why endure another day of a job you dread going to every single day??!
If it really is unbearable to you, simply let the parent know & wish them the best in their Nanny search.
Your employment is totally at will OP.
And if you cannot handle things, it is best for all sides if you just leave now.
Waiting even two weeks just adds two more weeks of misery to your life.
Best to move on.
Right now.
Good luck.