This child is not mine. The mother was 3 months pregnant when we got together. When the child was born I signed the birth certificate. We later married but soon after we separated. She claims she knows who the biological father is but since she has been receiving Welfare I am having to pay child support. Can I sue the biological father for child support?

No, You are the one who decided to commit fraud and sign the birth certificate knowing you are not the real bio father, but now you have to pay child support.

You can file in court to try to prove you are not the father by DNA test *** (MAYBE) depending on where you are at. In some areas there is a time restriction on how long you have to do a DNA test.