On the wrong side of these heartless gits

Well how do I start?
After a brief relationship with a girl, we seperated and went our own
ways. I hooked up with someone else who I fell for and married.
I recently received a text message saying "Your daughter is 1yr old
today" and after a brief chat, discovered she's had a baby...without even
telling me she was pregnant.
The CSA got involved and decided that I should pay £440 of my £1500
wages..my mortgage is £600 and my other bills come to about £300, leaving
me £200 to pay for my real child and my wife's food,clothing etc. Needless
to say I'm now falling into arrears with loans that the csa didnt want to
know about, struggling to balance my bills and feeling pretty close to
complete financial collapse.
I have no issues with making an affordable payment to this unknown child,
but surely the mercenary attitude and complete heartlessness to my
predicament is going to cause them to very soon get zero due to my losing
all i have.
I've talked to them loads and got nowhere, is there anything I can do?
.