Are you using a thermometer with 2 decimal places?
I used to use a digital thermometer with .00 digital places as that gives acurat temps.
Your temp can change by .02 and a thermometer with 1 decimal place won't show that change.
You also need to take your temp ideally at the same time every morning. Other wise after 3 solid hours of sleep. You need to take your temp before getting out of bend and moving around as this won't give an accurate temp. It's your resting temp that you neeed. I used to set my alarm for 4am every morning and I'd take my temp and go back to sleep.
Also sign up to Fertility friedn so you can chart you temps. Alot of us BBT'ers use that site. it won't cost you anything unless yu want VIP extras.