Next Choice doesn't work the same every time. You may have gotten your period within a week of taking it last time, but that doesn't mean you were going to get it within a week again this time.
Here's a little more information for you on Next Choice:
11. Are there any side effects associated with
When used as directed, nausea, stomach pain, headache, dizziness, breast tenderness, or menstrual changes (such as spotting or bleeding prior to a period) may occur. Your next period could be heavier or lighter, or earlier or later. If your period is more than a week late, you should get a pregnancy test and follow up with your healthcare provider.