First enjoy your time off; those two weeks go by pretty fast.

Usually it’s the other way around, too hot. You might try touching the heater hose going into the heater core at the fire wall, if it’s not hot then it could be the water pump leaking out coolant but it should get hot if that were the case. The thermostat could be bad even though you changed it.

I hope the coolant is not getting into the engine, check the dipstick just in case. I've had that happen before, Head gasket.

Richard