There are a few things to remember with taking your BBT.
First, you need to take it every day at the same time, even when you've got AF. You need to take your temp before you get out of bed, before you go to the toilet, before you do anything!! As in roll over to switch off the alarm clock and in the same motion, reach for that thermometer!!
Second, it's more accurate to take your temp vaginally, but I always took it orally)
A very helpful website is fertilityfriend.com All you need to do is put your data every day and it will tell you when you've O'd and when to test, and once you've been temping for a whole month, it will help to predict when you will O next month. There's also a great "charting course" in the website that will answer every question you could possibly have smile
Your temp will go up and down a little bit before you O, but once you O it will go up and stay up, until it drops when you get AF, or goes even higher when you get your BFP
Good luck smile