Period 4 days late

My last period was June 10th and ended June 15th. I took a plan B on June 16th. I haven’t got my period yet and I’ve taken 6 pregnancy test (Clearblue, first response and $ store test) and they all came back negative . The last test I took was this morning, first morning urine and straight negative. (First response) . Is the plan b the reason my period is late? I’m getting mild cramps like my period is about to start.