How to measure basal body temperature..?

I've been taking my temperature every morning before I get out of bed. I'm using a digital thermometer under my arm. My book says to do this and if your temp is consistantly below 97 that your thyroid function might be low.

The temp under your arm is one degree lower than your mouth, but I don't think I'm supposed to add a degree because the book says do it under your arm and use 97 as a guideline. Mine has been 96.8 for 3 days and 97 one day.

I'm wondering if when you are asleep if your body temp drops then rises as you start to wake up? then rises even higher once you move? Today my husband woke me up out of a sound sleep to tell me it was snowing. I felt like I was a rock, reached over and grabbed the thermometer. My temp read 94.9!! I thought "am I alive?" LOL! After about a minute I did it again and it was 95.9, then again 96.4 a few minutes later. Is that normal??