I think your suppose to check your basel temp in the morning before you start your daily activies.Your body temp goes up and down throughout the day.
If you are trying to get preggers you should only be taking you BBT when you first wake up in the morning. You need to have rested for atleast 4 hours to get an accurate result
Do you actually take your temperature or just think it's warm. The definition of Basal Body Temperature is the temperature of your body at rest. Typically it's taken after you sleep because it's the most accurate then. I would assume it's high before you sleep because you've been up and moving all day long which does cause your body to heat up.