Mosfet as a switch problem?
Without seeing the circuit its a bit difficult to propose a definitive answer but here goes. I'm guessing your trying to switch the power out from the regulator rather than switching the regulator down to ground. 



The voltage from the input of the regulator is (LiPo battery), through a high resistance (1M0) is used to turn the P channel MOSFET OFF. With no inpt connected to the N channel MOSFET the 10k ensures it is OFF. With a digital HIGH input the N channel MOSFET turns ON and pulls the gate of the p channel mosfet to ground, turning it on.