Can I get a court order for my ex to take a dna test to prove he's my 4yr old sons father,he keeps saying he isn't and csa where no good.please help.

Yes you can and you should just go to your local probate court and they will set if all up for you

You need to get an attorney, you can check out legal aid if you have no money, or in some states a advocate of the court.

You will have to file for a order of paternity, child support and a child custody order, with a court order for a DNA test to prove he is the father.

This will be in courts of various names depending on where you are, but it will be the court that handles family issues.

You should be able to talk to Child Welfare Services (or whatever it's called in your state) and file for child support, listing him as the father. If he denies paternity, he will be required to take a paternity (DNA) test.