still no period... please read!!!

Kayla

so I took plan b on March 15th, my last period was March 6th to the 10th, so I was supposed to ovulate on the 19th, on the 20th I started spotting (from the plan B I'm guessing...) but that lasted till the 31st... My next period was supposed to start April 2nd... I took a pregnancy test on the 11th (yesterday) and got negative!.... was the spotting my period or What is going on?...