Trunk light won't go off

[Conquerer]

I have a 95 S14 and the light in my trunk won't turn off. I've taken it out for now since it drains the battery completely if I don't drive it for a few days (just got a new battery a month ago after the last one kept draining more and more quickly until it died, probably because of this), but what could the problem be?

What exactly makes the light turn on? Is there a specific switch, or where else should I be looking for the problem? I've had the car for almost two years now and it definitely was fine when I got it. I'm sure this problem started sometime in the winter because that's when my old battery starting draining unusually.