i do that sometimes. it's never posed a problem for me. i always get my withdrawal bleed a few days after the active pills. how many days has it been since you stopped taking the actives? are you concerned about pregnancy? cos i think sometimes women don't get a withdrawal bleed on the pill. i don't think it's common, but it happens to some people and doesn't neccessarily mean they are pregnant. a doctor told me this anyway.
Once i had an event to go to so i ran two packs together back to back without taking any placebos and guess what? my withdrawal bleed came anyway! even though i was taking active pills. apparently running packs back to back like that doesn't stop some women getting their monthly bleed anyway.
I suppose what i am getting at is that sometimes the pill does weird things! it's probably just cos you messed about with the usual cycle, so wait a few days and if you still get no period then ask your doctor to see what they say about it.