No, because if you signed the birth certificate you could be considered to be the father, whether you are or not. If you are unsure, you shouldn't sign the birth certificate at that time (because you can sign it later on), demand a paternity test before you start paying child support or ask for visitation. Instead of trying to figure out child support on your own you can file papers after you find out if the child is yours or not to legitimize the child (saying you are the father). I feel bad for the guys who are married, have their wife cheat on them, claim the child is theirs and then find out years later that the child isn't theirs. Just watch the Maury show - some of the moms of these kids don't know who the father is. If you are in doubt the child is yours, get a DNA/paternity test done before you agree to pay child support then you won't have the problem of paying for a kid that isn't yours. Most courts would say you are out of luck, because you could have done that before you started paying child support.