How worried should I be ??

My boyfriend and I had unprotected sex on feb 18. My period started feb 10 and ended the 13th which is a normal period for me. After we had sex we decided to take a plan b just in case the next day. So it wasn’t even 24 hours after sex that I took the plan b. And then a week later I started bleeding again. I didn’t really worry about it all until I had a missed period this month I was supposed to get it on March 10th. On my eve calendar it says I’m 11 days late. I know plan bs can do this but I’ve taken them before and I really never had a late period but I also never bled a week after taking it like I did last month. Should I be too worried ? I don’t feel nauseous or tired and I don’t urinate any more frequently than I usually do.