This might be a bit of a silly thread really but i know I've spent many hours searching for the elusive answer to when to test after triggers/boosters...
Apparently it would seem traces can still be in system a lot longer than you'd think! I'm 16dpo today and bt showed hcg of 2 BUT frer still picking up faint line. Also yesterday cb digi had me at 1-2 weeks pregnant (which would be15dpo and 8days past booster).
I had ovulation induction so 5000 pregnyl trigger then 1500 booster 4 and 7dpo.
Anyways, period arrived bang on 14dpo so onwards and upwards to next set of injections in a month or so (when we can save enough bloody money 
)