Jason and Dodgeman are both right. It sounds like you must have had a lot of air infiltration before. Air infiltration, i.e. drafty windows, etc. that let warm moist air out and dry air in, is a leading CAUSE of some houses being too DRY in the winter. You definitely have a MAJOR problem that you need diagnosed ASAP before you house and/or health is permanently damaged. In the meantime I would leave a couple windows cracked to try to mediate the problem temporarily. Dodgeman had many good ideas as to what might be causing this. My first thought was unvented gas heating appliance. TURN IT OFF - if you have one and buy a direct vent one. Clothes dryer vent could cause this too. Do you have a humidifier installed on your hot air furnace? If so turn it OFF. Do you have a gas furnace or major appliance that might not be venting properly and throwing carbon monoxide and h20 into your breathing air? I'm really curious as to what is creating all of this moisture - please post back and give us more info and let us know how this turns out. don't delay this is a bad problem.