Yes, Plan B can delay your
period, make you miss
it, make
it come early, and do other funky things to
your cycle. The sooner you take it to the unprotected sex, the more likely it is to work. Since you took it within the 72 hour time slot, you are most likely fine and just experiencing a side effect. Keep in mind the app goes based off an average and can't predict exactly when you ovulate, which is why it's best never to go unprotected.