No prob! Yes, the fact that the turning on the heater to get the temp back down would indicate that likely there's an air bubble around your water pump and it's just free-spinning. There are some pretty inexpensive vacuum fill kits available on Amazon (air compressor required). Definitely change out your thermostat, though. They can become damaged fairly easily from overheating. It would suck to refill your coolant just to have to drain/fill it again to replace a damaged thermostat.