I live in California. 11 years ago I agreed to pay support past the age of 18 for one child. My circumstanes have changed. New family, three small children, health concerns, and ex is now making almost as must as I. We the court hear my case and change the order to read termination at age 18? which is in 6 months.

Do you have a lawyer? I'd contact a lawyer and ask what he thinks your chances are.

I don't know the laws in the US, I hardly know the laws in Canada. From my understanding, in Canada, a parent only has to support the child after the age of 18 if that child is attending school or is disabled and not able to support him or herself.

We have many legal experts here, check back often, I'm sure one of them will see your question and respond. :)

What was the agreement and why did you agree for one child to pay past 18, is there a mental or phsycial disability?

But if your income has changed ( not just a new family) or more bills, But if you are making less, you can ask for the support to be modified according to income,
But I would assume you could try and alter the previous agreement

It depends on what sort of an agreement you entered into (and why perhaps) and whether it became a court order. What does the agreement provide for?

Without more it's pretty difficult to answer the question.

I agreed to pay until my daugther obtains a 4 year degree or until the court further orders. My pay has changed and so has the mothers. I signed this with no intent on being married again or having children.

I have tried to negoiate with my ex, but she has refused and going to court is my last resort. Do you think the court will listen and be reseasonable about ordering support to end at 18 instead to continuing until she gets a 4 year degree?