No, you're not 31% body fat. Calipers need to be used by someone very experienced with them because doing the measurement wrong can lead to a very large error in result.
For tracking body fat I would either a) go to someone who is very experienced and get the 7 site caliper test or b) forget the calipers and just watch the combination of scale, mirror, and tape around the stomach. If the tape goes down then you're leaning up even if the scale doesn't move. Best idea is to combine several indicators and look at the trend as a whole from them rather than relying on just one kind of measurement.
If you have access to a good tech with calipers though it can be very helpful. I still never rely on only one kind of tracking measurement though.