Gunce !BBT question

Carol • Mother to 2 lovely kids Liam age 9 and Penelope (Penny) age 1 , also expecting baby number 3 due September 2016 ! 💙💗
Here's my BBT I'm cd10 and due AF on 30th. For the last threes days my temps have been exactly the same instead of climbing . Is this normal ?
​I O'd on 16th  my chart is below