I searched all over google for the answers for this and most of them read that the PSU is at fault but i did the paper clip test where you connect the green wire to one of the black wires (ref: http://aphnetworks.com/lounge/turn%5Fon%5Fpsu%5Fwithout%5Fmotherboard%5Fthe%5Fpaperclip%5Ftrick) and the fan spins.
So i thought my mobo was having problems so i returned it, got a new one and i get the exact same problem. So i dont think it's mobo at fault.
I placed the motherboard over an anti-static grey clear bag (the one that you get for free when you buy a motherboard) just incase the case was shorting the motherboard, unplugged everything except for the RAM and CPU and the samething happens - it turns on for a second (I can see the fan spin) and then shuts down immediately. keyboard or screen is not even attached.
I found the solution my problem. I posted it below. Thanks for your help guys!