Discarding BBT temp on FF

When should you discard a bbt temp on fertility friend? I always take my temp as soon as I wake up and before getting out if bed, normally 8am. However, I am prone to bouts of insomnia, will often wake up at 5am and never know whether I will make it back to sleep or not so take my temp. There have been times when I took my temp at 5, did manage to get back to sleep and have a difference in reading of a whole degree centigrade when I wake up again in a few hours time. In these cases, which temp should I go with, or should I discard them?