Plan b !

Hi girls I’m a little scared that I might be pregnant. I had unprotected sex on 6/12/20 around 12pm, he came inside me a lot of times throughout the day ... I took plan b the next day (6/13/20) around 11:30am ( about 24 hours after unprotected sex). On this app it said I wasn’t ovulating during those days, but now the app says I’m 6 days late. My period is not regular either, there’s times where I i don’t get my period for three months or it skips a month. For the past week about to be two weeks, my breast have been tender, and I’ve been having back pain and feel nauseous and lightheaded. I read these are some side effects from plan b, but shouldn’t last more then a week. I’ve read it’s also too early to be morning sickness, but I still haven’t gotten my period. should I be concerned? I also don’t know when to take a pregnancy test due to the fact that my period is irregular. When do you all think I should take one ?