Taking Plan B within first 24 hrs gives more than 95% protection against unwanted pregnancy
. You got withdrawal bleeding after one week due to effect of the pill. It is quite NORMAL and natural phenomena.
Your next period will be delayed for 1-2 weeks due to hormonal
imbalance and mental stress
. However, I suggest to undergo one home pregnancy test to clear doubt about pregnancy.
After negative test, you can wait another one week to get period naturally. If you don't get it, you can take progesterone
pill to induce period.
Good luck and practice safe sex.