Id repaint the room if you have not. Then when it warms up open the window and keep the door shut.
Maybe peal some oranges and lay the peals around. Maybe use baking soda on the carpet, leave 24 hours and vaccuum
I use carpeet fresh. My boys room always smells like gym socks, its the only thing that helps. DO you have curtins? If so they need to be washed also.
My computer room is home to my cat box and it can smell funky in here. I have an automatic airfreshner that sprays every 30 minutes.