Hi Nat... you should start temping day one of your cycle, first day of your period, and it generally goes down from CD1 until ovulation (because of high estrogen and low progesterone), and then rises (because of rise in progesterone). It'll fall just before you get your period, or stay high if you are pregnant. You can't really start temping halfway through a cycle because you don't really have a 'low' temperature to compare it too. HTH.