Plan b & your period

I had unprotected sex the day I got off my period & me & my bf were worried so I took a plan b the next day. I had some spotting 3 days after I took the pill & it lasted about 3 days. Now it is time for my period to start & I am a week late... It says taking plan b will delay your period by 3-5 days but I'm a week late & I'm worried...should I take a pregnancy test or just wait it out?