It depends on what's normal for you. But your body temp goes up noticeably from the day of ovulation until you start. (You have to check it 1st thing in the morning, even before getting out of bed but you probably already know that.) If you have 18 high temps (starting from when you ovulated) than most likely you're pregnant. Hope this helps.
your body temp should always be above 80. If it gets below like 92 degrees your body could start shutting down