in my experience progesterone can postpone your period and mimic pregnancy symptoms. A mind F**K if you ask me. I'm on it now too.
I know it is awful. Think I am going to try a natural cycle next month.
I dont know about oral as my DD used suppositories, but the suppositories answer is YES, at least for a while. Vicious cycle, that progesterone....
I have been told that AF will not arrive until after you have discontinued your progesterone...When I got my BFN last MAy, I didn't get AF until after I stopped the progesterone supps and PIO shots..
I went to my calendar from 2 years ago to see what happened when I got BFN and was taking prochieve... It looks like i started spotting on cd 31 and cd 32, the following day AF showed her face... Ugh. But it looks like I stopped taking prochieve on cd 30. I don't know why I stopped but I did. I do know that if you get BFP you continue, or atleast I know I'm supposed to. In fact, I had to continue using prochieve til 17 weeks, argh.
Best of luck.