Are you currently attempting dormancy? Has it always been an indoor plant?

I agree with Petiolaris' diagnosis, it sounds like the plant is going dormant if it has always received natural light. Sarracenias are North American plants that need a dormant period in winter or they could die off.

So should I put it in the fridge? I have a flytrap in there right now and it doesn't look too great

And by the way, it was outdoors until about September

Where are you living? Is it too cold for it to be outside? I live in the Buffalo NY area and have kept my Sarracenias, VFT's,... in the attic, by a window sill, if that is an appropriate option for you.

I'm in Southern New Jersey right now. So should I leave it outside in the cold, put it in the fridge, or keep it in the windowsill?

If the windowsill provides cool air near it, down to at least 40-50 degrees, it will be fine for dormancy. Just make sure the plant feels the cold but does not totally freeze. The fridge can work, but it takes space and, like you indicated about the VFT, might not be the best option since mold can affect the plants. Ideally, you will want a well lit place that has good air circulation while providing cold conditions just over total freezes (over 32 degrees Fahrenheit).

I have let Sarracenia sit out in 18 degree fahrenheit over night. It seems to be happily in dormancy so I don't think occasional overnight lows tn the upper teens are particularly harmful. keep in mind though, I do keep them in my garage for most of the time.