make sure you have plenty of radiator antifreeze , if your low you will lose heat , can you tell if it is circulating ? check your hoses both going in and coming out of the heating core and also the radiator hoses , if your fluid is circulating you can rule out water pump, thermostat , fluid level needs to be at the right level, check to see if the radiator fans are turning on/off as it is supposed to. It is possible that your interior fan was working but not your radiator and took up the cooling of the coolant by radiating heat out of the coolant via the heating core and now they have both failed. do not drive in an overheated condition or you will be for a heap of trouble with the engine failing next.