Temps can be so frustrating, even if you write them down sometimes it isn't obvious when the dip comes. Here is a link that has a temp chart graph. This breeder says labor starts when the temp is around 98.2 or below.
Our Sofia had been all over the place with temps, but when I put it on the chart I saw there was no real "drop" until later. It made me feel better. Good luck.
www.debbiejensen.com/signs_of_pegnant.html