Taking care of EX'S kid. And paying child support for my 2 kids.?

I have been paying CS for years.And as well I have been taking care of this kid like my own(spending $$$).EX says she not getting enough support&wants more $.I just lost a good job bcz of her.I manage to get another job & she is pushing for more $$$.I do have a lawer and he is working my case.I haven't told my lawer about the kid I take care of.Is there a way I can use this against her in court?