Hi I have had a few cycles with 1500 pregnyl and tested out every time. It takes me 7 full days for it to leave my system after the last injection and always on day 8 I would get my period, and tests only start to lighten about 4 days post injection. I always use first response tests. I'm currently 20 weeks pregnant and on this cycle it just didn't get lighter so I thought maybe positive at 6 days post injection. By day 8 dark line and no period and confirmed by blood test 10 days after last injection. Good luck hope it's a true positive!