OPK only positive day of ovulation?

[Anonymous]

We're TTC #2. Used an OPK last month for the first time (when we got more serious about trying), but have been charting for a while (charted w/#1 as well). The OPK only gave me a positive the same day as my temp rise for ovulation, which obviously was too late. It was the CBE digital, so I know I didn't read it wrong. Has anyone else had this problem? Do OPKs just not work right for some women?