How can I deal with this unnacceptable situation?

In 2011, the CSA assessed my maintenance at £130 / month. I provided accurate accounts of income. However my ex-wife made an appeal to the Tribunals after 2 years of delays and cancellation a hearing was held on my absence and a decision was taken that the maintenance should be reviewed and the new payment is £830 and to make things worse it should be back dated to December 2010, a total sum of £22,000 in arrears. Toda I have received a letter from CSA to pay a monthly payment of £1120.

I am now overdrawn and the money I had (retirement lump sum) I had put down for the deposit for my new home after the Law court awarded her the former matrimonial home (worth £110,000 after paying mortgage). My daughter is 16 years. I am not able to pay this as now I am officially retired and I do not permanent job as a doctor and the only income is £341 from NHS Pension.

My current locum post will finish end of October, if I do not good another job I will be officially unemployed. Also the Tribunals hearing was in 2/7/2013, I have not received any correspondence about when I can apply for an appeal against the new payment.

Would be please, be kind enough how I can deal with unacceptable situation. I can not pay and I if I allow the CSA withdraw that amount of money I will in deep trouble with the bank.
Is any legal help available for me to sort this mess with CSA, it was their mistake made the original assessment.
Looking forward to hearing soon from you.