@KoratMommy,
If this is real, the first step is taking the copy of the pre-nup to a lawyer to see how watertight it is or is not.
Second step by whatever means needed begin to siphon household funds into an account only your have control of and you know about.
Even if your pre-nup is iron tight that would not stop a judge, as far as I know, from granting you child support and perhaps the used of the family home until the children reach adulthood. Once more, see a good lawyer.