I would assume this is more precise than an OPK? So, my dr office said my blood work showed I was surging on Saturday and that it was important to BD Saturday. So, when would I have ovulated? Sat, Sun or Mon? I am so surprised this month, I usually have a 30 day cycle but this cycle I bled for a few days from cycle day 14 and I went from having no follicles to (hopefully) ovulating one! I was due for AF on Saturday, but I guess I have another 2 weeks since I o'd. Really weird this month, but I hope it turns out to be good!