Tires and WI Winter (Help Please)

[gtilami]

Good early morning,
I am a somewhat new owner of an 07 GTI (nearly 10k miles), and I also live in WI. About a month ago, my LCD screen starts telling me my tire pressure is low and I checked it out and surely enough, it was about 3 psi off. So I filled it back up to 38psi (I believe).

I started the car up and boom, "Tire Pressure Too Low" and I was like "WTF?!?!" so I was thinking that it could take some time to adjust. Two weeks later, still no end in sight. Start the car and my Fast tells me he needs more air for his shoes. I have filled those suckers up so many times that I am starting to get sick. Would I have the possibility of a leak... in ALL 4 TIRES?

The temperature fluctuates from upper 20's to upper single digits, but having owned a previous vehicle of about the same sized tires (18" huffs) I never had to fill up my tire pressure so much before. Any help would be greatly appreciated.

P.S. I was driving back to school on Thanksgiving break and (on a freezing day and a bumpy road) my front passenger side tire area just goes "Thunk", nothing has happened since and was wondering if something may have frozen and just got reset?