Municipal — birth certificate

Address:

Mumbai City, Maharashtra

I born on 25/12/1979, morning 4'oclock, in manju hospital vakola, santacruz east, mumbai-400029.then when i was 2 years old i went to visit my aunty house in coimbatore, tamilnadu.i stayed there and start studying, so on my date of birth they put which day i visited to my aunty house that is 15.04.1979, not my real date of birth.after coming back to mumbai, we try to get my birth certificate but i didn't get it because my mom and dad were uneducated and doesn;t registered for my birth certificate.now what should i do.current birth date on my school leaving certificate is 15/04/1979.please reply how and what should i do to get my birth certificate.