Could The Absence Of My Period After Taking Plan B Indicate A Potential Issue, Or Is It Just A Side Effect Of The Medication?

I had sex on the 23 of January,just right after my period ended 19-22,I took plan B on the 27th,the following week Thursday I had brown spotting which later turned to blood,which soaked a tampon for a day and that the same week I had metallic taste in my mouth for about 2 weeks I took a pregnancy blood test a day before missed period and it was negativr that was on the 18 of Feb and till now no menses