When the hot exhaust contacts the cold air, condensate will form. that's the white cloud seen at the tail pipes of automobiles.. That's not to say that's the cause of the white smoke you're seeing..
The symptoms you've described are not all conclusive for a blown head gasket. Here's one step in diagnosing your problem.. Rent or otherwise, obtain a cooling system pressure tester.. Some parts stores will loan certain tools. Remove all the spark plugs. Remove the radiator cap and install the pressure tester.. Pump up the system and wait about 5 minutes.. While you're waiting, look around for a coolant leak. With the spark plugs still removed, crank the engine over and watch for moisture spraying out the spark plug holes.. If moisture blows out any of the holes, that means coolant has found its way into the combustion chambers.. Could be a gastet has let loose, also could be a crack on the head. Head removal and inspection are the only way to determine which.