I have oil heat in the Boston area. We get a tankful every 3-4 weeks, maybe more often. The house is a 5-bedroom cape. Last winter when oil prices were sky-high, we were paying over $1000/month to heat our home with the thermostat abound 69. This year with oil prices thankfully more reasonable, our oil bills have been $350-500/month, though the thermostat is now about 67. I'd have to look up the size of the tank and gallons used. Your oil usage sound very odd, unless you are mostly heating with wood.