Heater question

So now that the weather brings the need for the heater in my car I have a question about it. I used to start the car up in the morning to let the inside warm up but noticed it was not getting warm inside until I'd start driving for about 5-10 mins. Now I recently figured out that if I have the heater blowing down at my feet it warms up very quickly but if I have it set to blow in my face or my face and feet it takes a long time to warm up. Now what I think is going wrong is that my thermostat is stuck open and the coolant rushes in before my engine is even warm. I've also noticed my temp. gauge barely gets to the C by the time I'm at school which is a 5 min. drive. I have the thermostat in hand ready to be replaced but I just thought I'd post to see what kind of suggestions I may get.

Thanks...