Next Steps

Has anyone taken Provera to start their period before? Show many days late on my period should I consider taking it? I’m 16-18 days late right now and have only had negative pregnancy tests thus far. I did a blood draw at 6 days late and it was negative also. I’m trying to stay hopeful and think maybe I am pregnant but not as far along as expected. But I’ll starting to feel discouraged and figured at least if my period starts I can start the process over. My last pwruod was 8/14-8/18 after finishing my birth control pack the week before.