I live in Boston and I avoid putting on heat until December and when I do - I put it on 55. I am "cold-blooded" like you so I will tell you my strategies.
You really need some wool garments. Cotton does not keep in heat at all. You say that money is tight so you are going to have to go to thrift shops and used clothing stores.
What I have on at the moment, is a silk knit long underwear turtle neck, these are very thin but heat-retaining. Over that I am wearing a lightweight, long (to my behind) cashmere sweater that zips up the front and has a hood, I have the hood up. On top of that, I have on a wool cardigan. And a down vest. When it really gets cold, I will add a lightweight down jacket.
I am also wearing fleecey sweat pants and wool socks.
I did not spend much on any of this, but I have been accumulating my woolies for years so have a lot of them. I go to used clothing stores often, even in the summer, looking for good inexpensive winter things.
I would say the first item you should acquire is a tightly knit wool turtleneck sweater. The turtleneck will help prevent heat escaping upwards. Second item, another wool sweater to go over it. Then some washable wool socks, a goose-down vest or jacket, and something for your head.
Avoid cotton, at least on your upper body. Wool,silk or down only. Wear multiple layers.
Explain to your parents how uncomfortable you are and ask to be brought to a good used clothing store. Spending $40.00 or so on a selection of woolies is a bargain compared to how much heat costs.
I live in Boston and don't know where you are so I can't suggest a place to buy good-quality used. I shop in several places around Boston and some of the things I have bought in thrift shops were actually not used at all, I guess some of my things were gifts that someone didn't want so they donated or consigned.
Someone else mentioned exercise. It is true that if you go for a long fast walk it heats you up and your body stays warmer for a good while.
I haven't done much yet today but as soon as I get moving, one of my layers will come off.
For night, you could ask for a gift of a down comforter. These are ordinarily very expensive but there are some outlets where you can get them sharply reduced. Example:
http://www.overstock.com/Home-Garden/Heavyweight-500-Thread-Count-Siberian-White-Down-Comforter/3507286/product.html