Ovulation test help!

As I've said on other posts, I'm new to using Opks. So I've been using the tests for 5 days now and I'm thoroughly confused. I had a spike in LH according to the test yesterday afternoon, but it wasn't peak. I was curious to see if the levels had risen so I tested again last night. The results confused me because now it's barely registering. I tested today and the test line is even lighter than last night. Any one know anything about this or why it would happe this way? Could yesterday have actually been a positive and the test just didn't register it that way? Any and all help is appreciated!

Thank you.