False positive OPK?

Crystal

Hey ladies. I am so confused right now. I have been doing OPK tests 3 times a day for 6 days now and I finally got a positive at 2:40pm today. But I went to test again at 6:15 and it's faded already. Is this normal? Or was this a false positive? TIA.

This one is 2:40pm

This one is 6:15pm