Help with BBT

Alex • Ftm to my little prince👶🏾💙. So blessed!
This is my 2nd cycle ttc after being on birth control pills for 12 years due to painful periods. AF showed this morning ?. I am currently using clear blue digital ovulation and recieved 2 peak and 2high fertile during my fertile window. 
I would like to start temping but i wake up at different times throughout the week. Do you have to take your bbt at the same time everyday for it to be accurate? Or as long as you take it the first thing in the morning before movement will it be accurate? 
Any advice would be appreciated