pregnant??

i just had unprotected sex on thursday and i was using this period tracker “flo” and now i don’t know when i’m supposed to get my period. I took a plan b yesterday and i know it can delay your period a little bit and this app it says i start tomorrow. I really want to avoid taking a pregnancy test :( but I guess i should if i don’t get it by next week? My last one started on dec 4th and ended on the 8th