2004 Honda Civic temperature problem?

My car has had some overheating problems in the past, the radiator, thermostat, fan relay and sensor have all been replaced. It's cold now, and I had been having problems with my heat not running correctly. It would go cold when my car would idle. Today was doing some highway driving, and the gauge kept getting close to hot and then going back down. Is this a heater issue? Or something else underlying?

Low coolant level
worn or rusted water pump impeller
restriction in coolant passage
blown head gasket

Sounds like a leaking head gasket to me.