Can plan b do this?

I took plan b feb 1st and got my period like normal on the 18th. I'm now about 12 days late for my period and I have been cramping bad and having sore boobs (like normal before I get my period) for those 12 days but still nothing. I also had a brownish discharge a few days ago that looked like my period is starting but that stopped. Can this be because of plan b? I've had unprotected sex maybe 4 times in the past month as well. I've taken plan b like two years ago and I've never been this late. What should I do? :( should I stop stressing?