Here's a breakdown:
* dagul (Kapampangan) - malaki (Tagalog) - big, large
* ka (Kapampangan) - ka (Tagalog) - you
* anta (Kapampangan) - pala (Tagalog) - (used to express surprise)
So, the sentence "dagul ka antak" literally means "you are big pala". However, in Tagalog, we usually use the phrase "malaki ka pala" or "ang laki mo pala" to convey the same meaning.