It could also just be an adjustment period due to the shorter days. My riding has also dropped way off but it's colder now, it takes more clothes to keep me warm on (and off) the bike and with commuting I don't feel like taking 10 mins 4x a day to change clothes, plus I'm "nesting" more: knitting, sleeping a little bit later on the weekends, wanting to settle down more than be active. I'd say just go with your body flow - it'll let you know when it's ready to be active again!