I feel like we get a lot of incorrect advice about our cycles from sources like the web, tv, and even our gynos sometimes. We should remember that our bodies are filled with hormones that are doing crazy things all the time. If you normally get your period on the same day each month, well good for you! But that actually puts you in the minority of women whose periods fluxuate every month. Typically, you are on a 28 day cycle but the idea that on the 29th day, your period will arrive is one which has been falsely constructed. It actually is meant to arrive in the 7 day period AFTER the 28 day cycle. Also, in terms of the morning after pill, this is basically giving your body a huge dose of hormones. Your body (and your complicated, fragile cycle) will not surprisingly often react a bit bizarrely, arriving late or early. I have taken the morning after pill and gotten my period within 24 hours. I have also taken the pill and been 14 days late. Neither were due to pregnancy. If you continue to take pregnancy tests which come out false, there are tons of more likely reasons your period is late (ironically, often because of stress which could be from worrying about your period!). Other reasons are changes in schedule, fluxuations in weight, or changes in medication.
Just remember, ladies, our bodies are very delicate balances of hormones and timetables which are sensitive and responsive to everything else going on in our bodies as a way of healthy self-regulation. The idea of timetables are pretty much our own constructions. Just give your bodies a break and let them work out the kinks of the excess of hormones they get through the morning after pill.
If you would like to induce a period, however, I have had very good luck with parsley infusions 4 times a day and 1500 mg of Vit. C twice a day. The former will try and put your body into the right state so it can begin to menstruate. The Vitamin C can induce abortion, though, so be careful with this one. Also, remember that in order for your body to menstruate properly, it must have completed an entire ovulation cycle. If that happened late, than your menstruation will follow suite about two weeks later.
Consider all the options before jumping to the worse conclusion. If you are using condoms and emergency contraceptives when needed, and keeping on top of pregnancy tests, you should stop worrying and let Mother nature take her course.
Hope this helps