Turns out that even though the winch came with a relay to prevent the draining of the battery, it was the culprit. Unplugged it two months ago and it has not lost any battery power since. I plan on making the connection whenever I know I will need the winch and then unplugging it afterwards {[I don't use it much]. I thought about rewiring it, but decided against it since the winch has only been used once since December 2019.