late second period after taking plan b?!?

Last month me and my boyfriend had sex and the condom broke but he didn't cum in me. (We've had sex since but with a condom and he pulled out before he came) But just to be safe I went and took birth control within the hour that it happened. I then got my period for that month but it was a lighter then usual. Now it's the next month and I'm a day late. Should I be worried?