My ex is making child support payments yet I'm receiving very little of it

When I first started getting child support 4 years ago my ex was paying $200 a month. I was receiving payments every Tuesday, on Tuesdays they would put $50 on my child support Debit Card until it added up to $200 at the end of the month. In January I got a letter from Friends of The Court saying that my child support case was cut off. This was the fault of my DHS caseworker, she was supposed to do an update interview about my Medicaid Assistance but never showed up. She closed my Medicaid case claiming that the reason was because I was the one who didn't show up to the interview. I called her several times and left several messages until finally after a month she did the interview with me and cut my case back on. Ever since that happened my child support has been getting lower and lower. I went from receiving $200 to $20 to $10 and now $7 dollors a week in child support. My ex has the same job and has been making the same $200 dollar payments only I am not receiving the payment. Two weeks ago my ex made a $300 dollar payment and showed me on his phone the proof of the payment but nothing came on my Debit Card. If he's making the payments why am I receiving so little of it? Why didn't I get the $300 child support payment?