If you were born in Delhi, you or your authorized agent can get a birth certficate from the Registrar's office. There is New Delhi statue under which child name on the birth certificate can be added. It takes a week or so. Cost is not much. Get several copies and they will all be original. You will need a copy of your original/old birth certificate. Then they can easily locate your info in the Register. I got is done for my daughters when they were 17+ years old.
http://delhigovt.nic.in/dept/pubserv/BirthCertificate.asp
http://des.delhigovt.nic.in/Vital/charter.htm
Click above link and under
9. IMPORTANT FEATURES OF DELHI REGISTRATION OF BIRTHS AND DEATHS RULES, 1999.
C. Entry of Name of the Child in Birth Record
Rule 10)
a) Registration on or after 1.1.2000
i) Within 12 months from the date of registration
Nil
ii) After 12 months but within a period of 15 years from the date of registration
Rs.5/-
b) Registration before 1.1.2000(Eligible period is fifteen years which will be reckoned w.e.f 1.1.2000
Rs.5/-
So I think you have until 2015 to get your name added to your Birth Certificate...