Back support

I live in Indiana and have three grown children past the age of 18. My youngest is now 23 years old. My ex was on disability for the last two years that support was owed to me so I allowed him to forgo payments with the assumption that he would catch up when he returned to work (he had asked me to help him out as he could "lose everything"). He had missed payments through the years intentionally around holidays and birthdays to free up the funds for himself. Five years later and he refuses to admit that he owes me for the two years that he was "allowed" to get by without payment. I've heard that I can collect from him for up to ten years past the child's 18th birthday...is this true and how would I pursue this?