Two weeks ago I took the next day pill 40 minutes after, even thought I didn't have sex but because I got scared of an activity I did with my boyfriend and because I was starting my fertility window. I didn't bleed days after. But today I had a brown mark when I went to the bathroom. I'm schedule to have my period on March 6. Could it be because of the pill? I want to think I'm not pregnant, a few girls told me basically that it's stupid to think that but as a girl who got the pill for the first time it's scary and I don't know what to think

Please help, I'm kind of scared.