hi listen sometimes you loose water by having a lick on any pipe and when your car is on idle you won't notice the lick. But when driving it rises the pressure then the water goes all out. but if you said that your oil is looking grey and not black your engine is mixing water and yes your head gasket as gone. but check careful top up the water and take a round the block if the water goes away it will be a lick on any pipe, normally it use to happen right around your inlet manifold. good lucky
raul
September 2010