Clearblue Digital OPK

Confused! I tested this afternoon around 1pm & I got a smiley face. Just for the heck of it I tested just now at almost 6pm and got no smiley face. Now I'm confused & don't know if I'm ovulating or not. 
​I'm having some sort of cramps today but I don't know if I usually have these during O cause I just started tracking it last month. Not sure what the heck to count is as. Has this ever happened to anyone?