Why were you taking them if you don't mind me asking? were you taking them after ovulation, possibly for a low progesterone issue? Or were you taking them to 'jump start' your period after being late?
Either way, for the most part, it won't delay your period. If you are going to start, you can start while you are still taking the progesterone. If you are taking it to 'jump start' your body needs to have the 'withdrawl' effects so it is best to give it a week before you call your doctor (and you are testing negative).
Have you tested? If not I suggest you do that. The progesterone will not effect the results.