Pregnyl shot

Ally • Married 12 years, 3 boys, baby #4 due 08/22/19
I had a pregnyl shot on CD 16. I am curious as to when a positive HPT would be accurate? 
I've been testing with an OPK, and HPT (Wondfo brand) everyday, to test it out of my system. 
However, I was thinking if the trigger shot can stay in your system 14 days, a pregnancy a test should show positive at that point anyways.  
 
I suppose I will have a blood test, if AF is a few days late?! 
Any thoughts?