postive opk on cd10 and six days later a peak on cbfm???

Hi,

I've been using the cbfm for the past two months (after using it last year before a failed IVF). First month 16 days of HIGH readings, no peak-I exptected that as I hadn't used it in a while. This month I used the cbfm in the morning as well as CB opk in the evening. On CD10 I got a smiley face on the opk and a HIGH reading on the cbfm. I stopped using the opk's and continued with the CBFM per the instructions. Today, CD16 I got a PEAK on the CBFM. I'm a bit confused. a peak reading 6 days after a positive opk?? Can anyone explain how that happens?