plan b and late period

me and my boyfriend had sex on july 15th and he came in me, we went and got a plan b less than 30 mins after i took it and that was that. my period was supposed to come last week on the 3rd and it’s been 12 days i’m worried on if it’s just gone be super late, if i’m gonna miss a month, or if i’m pregnant but i don’t feel pregnant. last saturday we went a got a test and they both came out negative. what to do?? pls help