Short luteral phase, late period , negative hpt

Brittny • 1 1/2 yr old
So I know there are topics like this all the time but, I have a short luteral phase and am currently 12dpo and 2-3 days late for AF (even for a Long cycle as they can vary), had 2 days of really high increased temp dropped by half a degree today and got BFN 
​Do u think I tested to early? Or am I out for this month? Anyone test at12dpo get BFN only to get BFP later?  (Used clear blue digital when testing) thanks for any encouragement and honesty:)