can an ex wife of 13 years come after me for child support while I'm the one paying and caring for the child and joint custody?

Do you have existing court orders for child custody & support?  Do you have 50/50 physical custody and is that part of the order?  Child support is calculated based on a number of factors, the majority of which are: income of both parties & percentage of time with the child.  There may be other factors depending on your specific situation. If you have been served with a Request for Order, you will need to respond to it.  In court you will need to substantiate your income as well as time spent with the child. Always remember, if your existing court order no longer reflects what is currently happening, you need to alert the court of the change by filing a Request for Order.