Deadbeat Dad. Back child support?

I have a 7 year old son. His
father and I were engaged but
never married. He abanoned us
when I was three months pregnant.
I had no contact with him until my
son was 1. He has seen his son
only about 15 times his whole
life. He never calls him. He has
gone for over 6 months wih no
contact. About a year ago I
forced him to pay child support
through child support recovery.
Now a year later he serves me with
papers wanting to legitimate my
child. This man has a background
of drugs and DUI. I live in
Georgia Wher I recently saw an
attorney. He told me that it was
very possible that he could get
what he wants and that he is not
required to pay back support
because I Contacted the support
recovery unit. Please help. Is
this true. I was counting on the
back support to make him drop
this. Thanks