My ex-spouse never told me I had a child for over a decade. Will this be taken into account for my support amount?

Generally speaking, support orders can go back two years. If you didn't know for 10 years that you had a child, you wouldn't have to pay child support for the full 10 years. You can, nonetheless, make an equitable argument to the court based on latches and argue that because she took so long to inform you of the existence of a child, you should not be required to pay support past that amount of time, two years.