Can I get back overpayments to the child support office?

I was paying child support to my kids’ mother when she passed away recently. The kids came to live with me immediately. The child support was being taken out of my pay, so several payments were made to the child support office after the kids were living with me. Is there any way for me to recoup this money? Suddenly having my kids move in with me has been expensive and I could really use the extra funds to get them what they need for my house and get them settled.