Before you are jumping to any conclusions, make sure you inspect around your engine (like coolant hoses , the coolant thermostat housing, the mating area of the head and block where headgasket sandwiched) to see if any coolant leaking from or around those areas.. Next check each cylinder by taking out each sparkplug out and shining a light down to inspect if any moisture or coolant inside or on top of piston. Get access of a radiator pressure tester and test if pressure is holding and no air leaking, look on your haynes manual. Could be a thermostat or hose...hopefully not your headgasket.