Question Detail: When I was 12 years old, I entered the US illegally. Now, I'm 22. I married a US citizen 3 years ago and we have a 3 year old daughter. I have no criminal record.
Answer: Since you entered the US illegally, you cannot adjust your status in the US(unless you are 245i protected).
Here are you and your wife should do to get you a green card:
1. Your wife files I-130 visa petition for you;
2. Upon approval, pay fees at the national via center;
3. File 601A waiver with the national visa center;
4. Upon 601A waiver approval, continue the process to receive interview notice from the US embassy in your country;
5. Leave the US to attend the immigrant visa interview.
If you do not have any other inadmissibility issues(such as criminal record; public charge; terrorist connection; visa fraud; reentry after deportation without US government permission, etc.), you should be able to get your immigrant visa and return to the US with an immigrant visa.
I hope this is helpful to you. If needed, please contact an immigration lawyer for help.