Coolant...

[chrshaha]

if you are losing coolant, but you are not (yet) overheating,
you have a leak!

you should bring it to a shop and look for that leak.
my guess is, it's a very small leak, as you have not overheated yet.
shotgun replacement might not work, if the source of the leak is not among those parts that were replaced.
the leak might be in the engine block. what does exhaust gas + coolant look like?

google for common sources of leak in the honda civic 2008.

I'll try to get it checked out again and thank you! Sabi po nung mekaniko before, okay naman daw. Wala naman daw hangin at okay naman makina.