My house it to cold!?

This will be our first winter in our new house. It has been bitterly cold here in NYC for the past few days. I have my thermostat set at 75 when we come home at night which is usually around 6pm. Its set at 62 or 65 when I am not home in the daytime. It’s been fine & working perfectly. Now that it’s cold, my thermostat hasn’t moved past 70 degrees. I even turned it up to 80 and it went up to 73. Is there something I am not doing correctly? I’m freezing!!!