if it was the head gasket the car would be straining to run. u can do a compression test. check the tail pipe u can smell antifreeze there. i suspect that u have a stuck thermostat. stuck or sticking closed. the antifreeze isnt gone, in that situation its just stuck and cant move so the radiator or recovery tank would appear empty. check the upper hose to see if it gets hot when the car is running. possible leaks r at the thermostat housing, the hoses at the clamps. the water pump which u could hear the bearing. the radiator at the top where the plastic meets the radiator support. or if u have an automatic check the connection of the transmission cooler lines to the radiator. my radiator had a leak. see if the radiator moves easily back and forth when the car is off. i had a small leak that i thought was coming from the recovery hose but it was the top of the radiator. if the thermostat sticks open u will get no heat and the gauge will move up slowly if at all and will randomly move up and down. if its stuck closed it will rise to hot and stay there. the latter is the worse situation of the 2.