AllyB
Feelings of hypothermia can occur for a whole bunch of reasons, but one way to help fix it is by consuming not only a good amount of calories, but particularly protein calories. Protein in general is about 30% thermogenic in your body - 30% of the protein you eat is "wasted" and turned into heat. From my personal experience, eating certain foods has very significant effects on how warm I am. Raw almond butter is something that makes me feel warm immediately.
There are a number of factors that can lead to this, and it was probably a combination. Perhaps increased blood flow to your organs (so your skin felt colder, with less blood flowing to it), perhaps natural circadian rhythms (your body temp. rises and falls throughout the day) and perhaps your body just trying to conserve calories. Probably a combination of all of these and more. I wouldn't worry about it too much. :o)