Mixed messages from CSA could cost me everything

About 10 years ago I received a letter from the CSA stating I owed £19000 in arrears but if I paid £880 now to them this would be the end of the matter. I paid the mother direct with a private agreement until my daughter was out of education and in full time employment. (Now 20 Yrs old)

Over the past 4 weeks I have had 1 letter saying that my case was closed and my daughter is now longer entiltled to maitainance. then followed by 3 letters stating I owe £19000 and pay it now with the threat of DOE for £500 per month. No means test nothing. This will cost me my House and leave me with nothing to live on.

Any help would be useful.