I been playing the picc for around 3 months. But i'm still having lots of trouble hitting the 3rd octave G, G#, A, A# etc..... Any suggestions as to how to hit them?

The answer is sort of like the old joke:

A young guy arrives for his first visit to New York and stops a stranger and asks: "How do you get to Carnegie Hall?" To which the stranger replies, "Practice, my boy, practice." :-)

Seriously though, it may take a while for you to develop the embouchure control needed for the third octave of the piccolo. I'd suggest playing long tones. Start on a comfortable middle octave note and hold it. Then move a 1/2 step higher, repeat, etc. You'll gradually stretch you range so that you can hit those notes. Another important thing is to use good diaphragm support and keep the air moving fast. Don't blow harder or pinch your lips. Something else that may help is to practice playing whistle tones. That will help to train your lips to stay relaxed for those high notes.