period late by 12 days

Hey ladies I really need some advice,So me and my boyfriend did have unprotected sex and he did cum but I bought a plan B but he came three times inside of me,Just yesterday I start having like brown discharge and a lot of

Cramps But I never start off my period like that later on in the day I started bleeding but it was really really light,I checked again right now when I woke up and there’s nothing I’m those girls who get their period and their flow is heavy so this is not normal for me I also took a test 3 weeks after the unprotected sex and they came out negative and now it’s been a month and week since that happened