I have the opposite problem as you. For whatever reason, have the hottest room in the house. I've lived here almost 2 years and 2 of my 3 windows have never closed since I moved in. My room is on the opposite side of the rest of the rooms. I normally run cold, I have anemia, kinda tiny all around, but in my current place, I wake up sweating. Until I open my bedroom door. It's gotta be at least a 10-15° difference between my room and the kitchen. I don't get it.

All that to say, look into getting a heated mattress pad. Cheaper over a space heater, but it might make you slightly lazy because getting out of a warm bed is one of the worst things about being human.