If those payments were not court order then they will most likely be seen as a "gift." Try to collect all receipts, bank statements, et. I am in Missouri, FSD can have things messed up. Or your dh could have messed up. Most people from the last 10 years FSD is involved in child support collection. If your husband was suppose to be paying through FSD, hope the ex is nice enough to write a letter correcting saying he has paid. If she does this keep that letter forever! One audit can come and haunt you years down the road (my mom and dad had this issue).
I would get a lawyer and stop paying her directly. Bank the money and make a lump sum through FSD. Sadly, the last 10 months might have been for nothing. FSD usually will take the MOST amount over money to catch up as quickly as possible.
It is not unheard of FSD to have the wrong numbers to figure it out. The last paper work I got asked me how much I thought my EX made. I have had more than one friend run into this issue. EX thinks they make more than they do. One ex got pissed because she filed for an update because she thought ex got a promotion when he took a demotion and a pay cut to keep a job. Her child support was adjusted down.
Our old neighbors, went a few rounds with FSD because their court order had him paying (buying) the house she and the kids lived in verses paying child support directly. This worked for her because of the four kids only two was biologically his. The house payment was more than child support for the two kids. He wanted this way because he loved three of the kids dearly. The forth, was not his and the reason they divorced, proof she was having an affair. However, he didn't want his kids or that child on the streets. But this non-traditional child support arrangement didn't fit neatly in FSD framework.
Another friend found out that the man who loves her daugthers (bio dad of one) would be screwed royally if she went through FSD even if she signed affidavits because things were seen as "gifts". They had an amicable arrangement until some set a bug in her that she would get more. FSD only figured one child in, because the other was not his biologically. Between his family, his taking a different shift, and her family their was never a need for day care. He paid for sports, clothes, et without thinking. He would buy "extra" food if he thought she needed it. When she lost her job he paid her car payment. He had a debit card for medical expenses, since dd 1 was not biologically his it made since for her to carry the insurance -- she never had to ask for any of this. He paid for school lunches, et. She had to come to a screeching hault when she found out this stuff was going to have to stop, because he was going to be nailed with not only current child support but 6 years prior child support for ONE child. Then once he was caught up she would get support for ONE child. His pay would be reduce because he would have to get insurance on that ONE child which her insurance covered. FSD and a nasty lawyer wanted to nail him for back medical, you name it.
Another coworker found herself in trouble when she went for chemo. She was in the position either pay for child support or chemo. Her ex finally said screw it with trying to get a modification with FSD. He gave her the debit card that he got his support on. FSD saw that she was still making money so she should be able to pay. Even if they were still together this would have been a financially strapped time for the kids. In the long run, Chemo was more important to the kids if it meant having mom around longer. But FSD has rules, not common since.