@jennifergamble1,
If you're unable to afford the payments, I'd see about revisiting the amount in court. Truly, you shouldn't be falling behind - she could be depending on that money and whole budget (and their activities, etc) could be thrown out of whack. It's just not fair. It's also not fair for you to pay such a huge percentage of your take home pay for support that you can't have a decent life yourself.
I would go to Legal Aid and ask for a hearing. And also to deal with your daughter's mother. It may cost you upfront, but it'll save you in the long run.
We all need to live a decent life.