Slipped up by giving ex cash

I gave my xwife cash so can not prove it only that i took out £650 form a ATM.

Went to court but could not do any thing about it CSA did not want to hear what i had to say and the court said your childeren pay for them so now i get £649 plus £1 abm fee from my wag.

Dont even see the money been doing this for over 4 year and still got 3 years to go At one stage i was giveing the x cash and i payed for her car so see could take the children to school.