When I get my weight down to near 'race weight' I get cold all the time. I find myself checking the thermostat to see if someone turned it down, and pulling the extra blanket over myself at night that is usually just for my wife. I'm pretty sure this isn't a difference of insulation from an extra layer of fat because I'm talking about maybe 5 lbs of weight. I'm wondering if it is my metabolism slowing down to conserve fat. Anyone else notice this when you get skinny? (And note that I don't get super bike racer single digit bodyfat stick insect skinny, just a shift of 5-8 lbs annually from off season to race weight.)
You could take your temperature, I doubt it is actually decreased.
You ever eat seafood? You could have low iodine / mild hypothyroidism but all this would be detected with routine blood work.