What were your temps before O?
day 18 is when ovulation is about to occur. 24-48 hours there is a chance that you concieve. your body tempture has risen that is when you take an ovltion test.
well before they were in 96.80 and then on oct 11th droped to 96.31 and i had positive opk that morning the on the 12th went up to 96.80 then the 13th 97.50 . then 97.0 then 97.6 so ya see. its crazy but the stayed up above cover line untill 7 DPO then went down to 96.88
I still think that sounds very promising. It seems like you can still see a bi-phasic trend, with lower temps before o and higher tems after (even with a few single dips). I would give it a couple more days and then test again. Good luck!
(By the way, the dip at 7 dpo could be an implantation dip!)