Some of the causes include cold exposure, alcohol or drugs, shock and some metabolic disorders like diabetes and hypothyroidism. Overwhelming infections like sepsis may also cause extremely low body temperature.
I have low blood temp also. I lived up north US could not stand the cold. Moved to the south love the heat. But I believe your temp is with in the range of the human body. It's hard to get anyone to believe you when you run a fever because you run at a low temp.