try sleeping under a electric blanket on a heated water bed!!!
i did that for a few winters in a wood heated cabin.later i got rid of the water bed and slept in a down sleeping bag with a wool blanket over it.the cold coming up from a mattress in a unheated room is the killer.sleeping on top of layers of wool blankets helped but i had some nasty back spasms until i moved to a real house in the city and a bedroom that was kept a bit warm so the mattress did not hold the cold.