Sure it could be the water pump not sure how exactly to test but if it is not leaking and not making noises and the shaft seems tight (not bad bearings) then I would try this first (assuming you still have no heat). Pull the hoses off the heater and flush each way a few times to make sure its not blocked. Other than that I guess the pump is next. You thermostat is opening?

 

Check your thermostat. If it is stuck shut, no coolant will flow and you will overheat. Also check for leaks. Get a coolant tester it goes on the expansion tank in place of the cap. You pump it up to factory pressure (usually no more than 15psi and look for leaks or the sound of escaping air/coolant. I would replace the thermostat and bleed it according to Spikes link.