My girlfriend was pregnant by another man when we got back together do I still have to adopt the baby or is she mine already?

If you are on the birth certificate, you are the legal father. However, if you acknowledged paternity knowing you weren't the father, you may be guilty of fraud. The mother or the bio father may be able to challenge paternity and have you removed.

The laws vary from state to state.It depends on your location.

Agree, at this point you can not adopt, since you are the legal father. BUT the actual father will still have rights, and those rights vary by state, as to how long he as to act on them.

Again if you knew this when you signed, you committed fraud on a official government document.

So now you can do nothing but wait to see if the real father ever challenges it.

Well its in Missouri and we didn't know it till she started looking more like him. Certain features on her face etc.. But when she was born she looked like our eldest daughter. She still does but a few facial features.