Am I protected? Please help.

The last day of my last period was Tuesday, August 25th. I took my first pill on Tuesday, September 1st. I had unprotected sex on September 13th. Was I protected by then or do I need to worry about plan B? Because the paper with my birth control says if you take it the Sunday after your period you're protected after 7 days. What if you don't start it the Sunday after your period? Does it take longer to work? Because I remember when I first got my pills in December the lady mentioned two weeks for them to start working. Help. Any input helps. (I'll probably just end up blowing the 30-40 bucks on plan B just in case)