If you can rule out health related issues then try:

Multiple layers of clothing, have tops and trousers overlap so that no cold air slips in. Hot beverages and food help as well. If you can spice your food hot. Eat enough, I get cold if my body is lacking something to convert into heat, then at the latest I eat. Do you have insulation between your feet and the ground? Try shoes or blankets/pillows (wool does an exceptional job) If possible wear any form of cap under your headset or get a hat to cut into shape so you can wear your headset, one loses a lot of heat through the headsurface. Is your chair comfy and warm, or does it drain heat? Pit a wool blanket on it. Regular exercise (through our the week) helps a lot

That's stuff that helps me survive winter, I am sensitive to cold more than I like to admit...