Also, just because you're paying child support, doesn't mean you're not spending any money on the kid on top of that, before anyone jumps in with "ERMERGERD HOW CAN ANYONE LIFE OFF THAT!" Newsflash, there's also another parent who should be paying for their own household expenses, and half the care costs.
---------- Post added 2012-12-02 at 09:40 AM ----------
I know there's groups out there who are willing to help with the costs of getting lawyers for things like this, too. I'd look into that, see if there's any in your area.
Also, what's the custody agreement? If there's a court ordered agreement in place, she can't just stop honoring it and say "nope, she's going somewhere else since I'm getting less money now." (What a fucking cunt, by the way.)
Keep receipts of everything you buy for your kid, and a log of all hours she's with you, and bring it to the courts, ideally with a lawyer.
Your case is definitely everything that's wrong with child support courts right now.