Bbt question before i go crazy

Jennifer • Angel baby in my heart 27/01/017 married 01/03 rainbow baby in way EDD 15/12/2018

Ok so i was always told to take bbt when you had three hours sleep. For me i tend to wake up durning night so i saw i had three hours. Took temp.. went back to sleep woke up lager on and took ye,p,again to see i had longer sleep time

What one will i go by

One had a low temp

Last one took a huge spike.....