First thing to understand about most BF% measurement devices is... they are approximations! Unless you go into a hydrostatic displacement tub, you will only be seeing rough approximations that may or may not work for you based off of your body type. The best way to combat this is twofold:
- Use multiple methods to measure your BF%.
- Be consistent and with your measurements.
By using multiple methods of calculating body fat, you are far less likely to have your results skewed by a single inaccurate measurement or outlier. Maybe you measured in a wrong location, or maybe you pinched the wrong fold of skin, resulting in a slightly higher/lower reading? The larger your sample size of measurements, the less you will have to worry about these questions.
By being consistent with your measurements I mean two things. You want to measure in the exact same place you did last time, at the same time of day, with the same amount of food/water in your stomach, etc.. This is most easily accomplished by taking your measurements first thing in the morning before you shower. The more variability you can eliminate, the more accurate your readings will be.
Personally, I recommend using the navy body fat calculator, the mirror test, the caliper test (both 4- and 8-point). You can read more about different measurements in this question.