text: File a motion for modification.  I don't know how it is in California, but in Colorado, the forms are readily availible online.  Note in your petition how many overnights you have, and document the money that you are already paying her.  Get receipts, bank statements, etc.  Probably like most human beings who don't live with a lawyer by their side doing running commentary, you didn't get receipts from her, but gather up all the witnesses you can.  Note: I don't blame you for that, but the lack of evidence might hurt you.  \nThe courts usually don't care about your expenses (sad, but true), but on the whole, they can't take what isn't there.