Digital OPK- false result??!!!!

I always check the inserted test stick after receiving the results and it never seems to be darker. Actually the day I got the smiley face was the lightest day on the test stick! Does anyone get a smiley face and then check the test strip to find it not look positive. My positive result actually looked like blue smeared dye. Nervous I should keep trying with the smep until I get another positive!