I did one of those body fat % tests once and it kept saying error... They said that's because I had less than 3%. I did one a few years ago and I was up to like 10% then.
Were you using bioelectric impedence to measure? If you were those measurements are completely worthless. Assuming you don't have access to extremely expensive equipment needed to do a highly accurate body fat %, calipers are the best "cheap"option.