i know this is an older thread, but thought i could maybe help for next time. i get a faint line on the answer strips 2 to 1 1/2 days before ov and temp surge. it's been like that for a few cycles, so i suppose it has to do with your body getting ready to ov. if you aren't in the ov zone quite yet, that could explain the negative clear blue.
i had my first faint line this cycle this morning, so i'll be getting busy tonight.
