Hi Bulrush,
You probably want to avoid cotton altogether. It will make you colder if you sweat while hiking. You might want to look at some heavyweight synthetic long underwear instead--something that wicks moisture.

At night, you might also want to heat up a water bottle full of hot water and throw it in the bottom of your sleeping bag a few minutes before you get in. This will keep your feet warm which will make you feel warmer overall.