Can you get a false positive on OPKs?

I'm using Clearblue Digital, and below are my tests. First is 2 days ago, second is yesterday, third and fourth are today. First 3 were taken at 2pm. The third (darkest) was today at 2pm and I got a smiley face. I took another one tonight (fourth) at 6pm and got a negative and the line is lighter.

Was today a false positive? Is that possible? Or did I somehow miss ovulation?

We bd 4 days ago, 3 days ago, and 2 days ago. We missed yesterday due to circumstances out of our control (hospital visit). Am I out now?