Your order should address the overage. The Judge would have made the ruling on when (if any) you were owed.
It is not actually an "overage" until the order says x amount and then you make the over payment. The Judge has the discretion on whether to make the order retroactive or not. They usually do, as was my case a few months ago on a modification. My case was 16 months old but he did in fact make it retroactive to date of filing and gave me a reduction per month for 5 years to allow the over payment to be paid off.
But again, it is not actually a true "over payment" until you pay above the court ordered amount. You in fact paid the amount ordered until it was changed. The Judge has to make the decision and put the remedy (if any) in new orders.
Men who fear becoming fathers dont understand that fathering is not something perfect men do but something that perfects the man. Its like an aged man reclining under the shadow of an oak he planted.