As the (married) mother of two children you have limited sympathy.
Sex leads to babies. Babies are children, teenagers, people.
You made a child, now you have to support it, or just be a total deadbeat dad- and then who will be calling who a 'bum'.
And yes, Child Support payments are a legal matter. She could (and should) take you through the courts.
That baby is 50% hers. And 50% yours.