Tammy, did you or the repairman replace the thermostat. It is very important that the thermostat be level if the temperture number you set and the actual reading are to agree. There is a mercury switch in many thermostats and these are calibrated in a level position. Installing them so they are not level means that they will not react correctly. The directions for this should have come with your new thermostat.
But I agree with David. You should call the repair person back and let him resolve this. If you replaced the thermostat, let him know and ask him to check it.
Our house has not been as warm as usual with the heat loss from this very cold winter. The thermostat only checks the temperature in one place in your house, usually near the center, the warmest area. When you get away from where the thermostat is measuring, your house can be much colder. One other common factor is that some houses have really warm second floors while the first floor is cold. A fan to move the hot air back down is a big money saver. I haven't seen your house and have no idea if this is the case, though.