Can the state charge back child support is the mother has not requested it?

I live in CA. I found out that I am paying back child support for three years of payments that are not in my order, nor did my ex request. Can the sate charge me back child support, if it is not in my current child support order, and was not requested by my ex. The child support says she is not entitled to back child support, and that it going to the state. She did receive aid for 11 months, which the repayment is in my current child support order, and is payed monthly. The court order I have is for a balance of $3540. This is repayment of while she received aid for our son, plus a current monthly payment for 295.00. She and I are trying to figure out why on the child support payment statement the balance started at 13,000.00, and has been payed monthly since 2005, never missed a payment, and it is only moved 1000.00 per year. She is addiment that she never received any money for three years, or requested it. how can the state take monies for back child support and NOT give then to the other parent?