My new ps3 wireless shock controller won't sync!

Had this red controller for about a month and then later it won't sync when I turn it on, just keeps blinking and it only works if I attach the charger with it, how do I solve the problem?

thanks!!!

On the back of the controller is a little dot thing put a pin or something small into it.It is the reset function on there after pressing that in plugged your usb into the ps3 and press the ps button it should work then.Hope this info helps ya out let me know if it does