If the case is a IV-D case (if filed through the prosecutor's office), you can find out how much child support you owe by calling the Kidsline at (800) 840-8757 or (317) 233-5437. Customer Service representatives are available Monday through Friday from 7:00am to 5:00pm.
If the case was handled by a private attorney, you will need to contact the attorney or go back to the original legal document and compare payments with what was ordered.