Progesterone help.

So the exact instructions I was given was take one 200mg vaginally 2 days after positive opk until start of menses( I called and asked back then and she said until your next cycle). Ok at the time it seemed like it make sence but now I am a day late and not sure what that means. No my cycle is not regular in the sence of I do not get my period exactly 14 days after ovulation. Is anywhere from 12 days to 20 days. I've been ttc for almost 2 years and this is my first time on progesterone. This is my 4th cycle of Famara (letrozole). I feel like it should be a no brainer but somehow it's not. Am I suppose to stop taking it? Or will my period start if I'm not pregnant even while on it. I know it is a drop of progesterone that send the singnal to start production of the other hormone. But I'm confused as to why the OB-GYN office wouldn't have told me special instructions. I want to call them but the only time I have during the day to call is on my lunch break. I have no service where I work so I'd have to use a work phone and we don't exactly have offices where I could shut the door for privacy. Does anyone have experience with progesterone for part of their fertility treatments?