Do you have to pay child support on a child that isn't yours? Fathers name is on birth certificate, but dna test would prove he wasn't the biological father.

First until there is a DNA test and proved in court yes.

After that, it will depend on the state. In some he may have to still pay even if latter proved he is not in some areas.

What state and Were you married to this person at the time the baby was born ?

Missouri. And it has to do with my boyfriend and his ex wife.

In most states if child is born to a married couple, the husband is considered the legal father unless a protest is made. Most states have a window of time in which either the husband or the bio father can protest. So there is a good chance your boyfriend will be held responsible for supporting the child.