csa overpayments

[myself37]

Hello,
I have been paying my csa payments for my son who lives with his mother, I work in a full time job and i claim industrial injuries benefit, due to an accident at work, i have been claiming that for nearly 9 years. On the CSA website it states that if you are in recipent of these benefits you only pay �5.00 per week, Does that mean that i only pay the �5.00 if so then i should be entitled to a refund as i have paid considerably more than �5.00 a week,
Does anyone have any advice which is correct as the CSA says because i work they have taken my wages into account instead of this benefit, i am not one to shirk my responsibility but i do wish the CSA could be more clearer in what they state.
Many Thanks
R