Is it normal for opk to be positive then a few hours later negative?

I know this is probably asked so many times, but Im new to this. This is my first time using OPKs consistently. The last two days I had negatives then this morning my first positive with ewcm at about 10am I just checked at 530 and it was a blazing negative. Is that normal and just mean I should be ovulating now? First picture is yesterday, second is this morning and the third is the one I just took hours after my positive