Am I on my period or not?

Hi everyone, last Tuesday I took a plan B pill for the first time because I was scared of getting pregnant. Between Wednesday and Thursday(I don't really remember) I start having cramps I thought it was probably the secondary effects. I started bleeding on Monday at school the blood was really dark ( I'll send an image for an example) I am scared if the bleeding was because of the pill, or it may mean that I am pregnant.

P.S.: Still bleeding today is the 3rd day