Mother of purl

I was minding my business, opening the mail, when HOLY SCHNIKES!  Our electric bill was $400.  Our house is 1286 square feet and even uninsulated, in the dead cold of winter, our normal winter electric bill hangs out around $180.  My first thought was we had a leak, like plumbing.  But a sweep of the house showed, our auxiliary heat has been on all the time.  Where the thermostat is, a shadow is cast on the bottom part of the display where the words aux is shown in size 1/2 font.  I checked the meter against the bill and in the last 5 days we've burned through the same amount of electricity that we usually use in a month.  We've shoved the temperature down and have hauled the kerosene heater out of storage.  I hope the heater fix it guy doesn't have to bleed us dry to correct whatever the issue is.