I did not know she was pregnant!

This all started 18 years ago when I received a phone call from a lady that said she was with "Jamie" (changed name of birthmother) and she had some questions for me. I was a little surprised since I had not seen or spoke to "Jamie" in 7 or 8 months. I thought she was gone to college and that this phone call had something to do with school. I answered several questions before they got more personal about me. I stopped her and asked her exactly what this was about. After a long pause she asked how long it had been since I spoke with "Jamie" I told her 7 or 8 months. She then informed me that she would have "Jamie" contact me. I soon learned that "Jamie was 8 months pregnant and that I was the father. Being only 19 at the time I was in shock and did not know what to do. I eventually agreed to sign all necessary papers. Ever since that day I have second guessed my self, a day does not go by that I pray I made the right decision. Now my daughter turns 18 in 5 weeks and I have no idea how to begin my search. I would greatly appreciate any help I can get. My first concern will always be her feelings and her right to decide if she wants to be in contact with her Bparents.