Want to be legit as my father's daughter,, pls help po..

What do i need to do..?

I was born year 1990 and i wasn't able to use my fathers name s birth certificate ko kc d cla kasal ng mom ko (my mom is married with her past relationship) , and d pde gmitin dw nung time n yun yung name ng father s birth cert.. Kya ang nkalagay lng ay name ng mom ko and n/a ang dad ko.. Sa kagustuhan ng dad ko n gmitin ang surname nia, from baptismal hngng s mag aral ako he let me used his surname.. I have a sister din n gnun gnawa nia n pngmit nia surname nia 1yr lng kc pgitan nmin d pdin pde gmitin surname pag d ksal pero nachange ng dad ko, nprocess n nia kya under n xa ng surname ng dad nmin.. My problem is ako d p nchange skin bec my dad passed away ,also our mom.. Pnu n ang nid ko gwin kung wla n cla pareho.

. Nauna maayos ng dad ko yung s kptid ko kc mas kinailangan nia for work, dhl ako d n nkpgtapos ; i got pregnant early at ang ngamit ko n name is yung may surname ng dad ko.. I just discovered that nung kinailangan ko mghnap ng work , need kumuha nso, and yun dun ko nlman n wla pla tlga xa birth cert ko.. Kya ang nkalagay n name ko s nso ng anak ko iba s totoo kong surname.. What to do? Pls help po