Is I am diabetic or prediabetic? Wrong.

Today I done a test at a camp .Firstly the blood sugar came 182 in glucose meter and I said It can't be possible so they rechecked it after just 1 second it came 170 with the same glucose meter is it possible to get such a huge difference in just 1 second? . That was a random test after 40 mins of the meal .then I got suspicious so after 20 mins I checked my blood sugar level from some other glucose meter it came 115 without doing anything  .should I go for a blood sugar test or the first glucose meter is wrong.i  am scared . I have become predidiabeticor I have diabetes. And in the month of June I have tested my sugar level it came 150 after eating rice and watermelon .I have eaten watermelon and rice just 20 mins before the test .please help.