How do I collect unpaid child support?

The father of my child has frequently paid less child support than he was supposed to and even disappeared for a couple years. Recently, we've come back into contact and he has been paying (almost as much as he is supposed to) each month, but he recently told me that now that my daughter is graduating high school and turning 19 in october he doesn't intend to continue paying me every month or paying what still owes me. He owes me over 44,000 plus maternity payments! I want to know what department to contact about child support collection. Also if you have any information, advice or websites that could help, please share.�I haven't taken action before now because I was trying to keep things civil for my daughters sake, but he's caused me alot of financial hardship over the years and I have to do something. Hope you can help.�