Plan b to late ?

I had unprotected sex on the 9th & 12th of this month , I took plan b on the 15th in the morning , I usually start my period anywhere from the 17-20 today is the 22 and on the 9th when I had sex it said I was fertile , and I still haven't gotten a period I haven't had anything at all not even spotting this is the latest my period has ever been like its never this late , could the plan b have made it late ? Or could I be pregnant ? When should I take a test ? comments please