Did I miss my positive OPK?

Laura
​I'm new to OPKs. I've been having what I think is ovulation cramping for the past 3 days but no positive OPK. I looked back at my tests and now I'm wondering if I had a positive OPK on day 12. What do you guys think? I guess I was thinking a positive would be glaringly obvious. Anyone have any insight on these things?