Where is the thermostat in your apt? If it’s in a well sealed room, it may not be getting triggered by the cold and not turning on. Locate it and come to a consensus with your roommate(s) re what is a reasonable temp to keep it. In the meantime, buy window sealer from the hardware store and apply to your windows. It will help. I’d also suggest getting an electric blanket. A plush one with auto shutoff will help.