CSA increased payments and did not tell me

I have 2 children aged 2 & 3 with my ex partner we have not been in a relationship since my 3 year old was 6 months old.

To cut a long story short it was not a pleasent relationship she was not a very nice lady she is 10 years my senior with 3 older children. since my youngest son was 3 months old I have been allowed any contact. I always paid maintenance direct to her sometimes £300 or £400 a month.

Since the breakdown & her non acceptance of the relationship being over she contacted CSA, which I have been paying £225 per month for both children which I have no contact with at all. Since then I have gone on to have a daughter with whom I live with and her mother. So I contacted CSA to inform them I have a daughter living with me. They lowered my payments to £214 per month.

Then this week I have a letter from CSA saying from june my payments will be increased to £53 per week & i am now in arrears, how could i know they had been increased in june if they didn’t tell me untill mid august?

So septembers payment will be £280 then £231 every month. So since phoning to say I have a daughter living with me I am now paying MORE!? how does this work? when calling csa i am told it was reassessed as my wage has increased who has a payrise in june? i had an annual bonus in may from 2008 & apparently bonuses are included in salary? Also out of the 2 children with my ex i am only on 1 birth certificate & not the youngest & there is reason to doubt paternity. csa have told me until i prove otherwise ie dna tests i have to carry on paying. even tho i have since gone to court spending £4500 in the process trying to get dna tests & access only to have my ex not turn up & refuse etc.

now i can’t afford to carry on & have a debt to pay off. Please help??? can’t see where to go from here?