What percentage is a state allowed to take from my income for child support. Also, if I am paying child support on my kids from a previous relationship, is that amount considered in a new, separate case?
Also, if the other parent refuses to get a job and do her part in supporting the kids, am I expected to support her as well?
I noticed that the state of Oklahoma bases support guidelines on both parties income, but if she doesn't have any income, am I going to be expected to pay more?

Yes, if she has no income you will end up paying more than if she has more income.

But the court can not require them to work, only make you pay according to each income.

Normally one child will be about 20 percent of your pay for current support,

If there is back support to pay there will be additional taken out.

I would like to ask did she have a job before? If so then they may be able to impune her income and use that as a starting basis.

Well that's the problem it's in Oklahoma. I was paying $640 per on a $10.00 hr job.

She had a job, where she was making 12 a hour, but she messed it up. Now she is basically living off her parents and expects me to support her as well as my girls. I don't mind supporting my girls, but why should I still be paying her to sit on her butt!!
I also would like to know, if she didn't disclose that I am already paying support on 3 girls from a previous relationship, can she get in trouble? I pay $800 a month for my 3 older girls, but I don't think they figured that in when they were deciding what I should be paying for the youngest 2.

It is not your ex's business to tell them anything about support orders you may have already had. That is for you to inform them of when you fill out financials. That way if there is a credit to be given it can be taken at that time. They should have informed you before just moving forward. That way there is a clear way to calculate the support. If her last job was at $12 per hour then they should if you ask for it apply that as her base for the calculation.

She is saying that my support was modified, but I wasn't involved in any calculations... she also said she got a extra 200 a month for medical bills that I haven't paid. As far as the medical bills, I haven't received not one, do they expect me to hand her over money that she "says" is for medical? I pay the insurance so I get a statement that shows when my girls have been to the doctor, and it's not near as much as she claims. Plus if I don't get a bill, then why should I take her word for it and send it?