so i took a plan b on february 14. i was supposed to get my period wednesday the 20th but didn’t have symptoms till the day after. the 21st i had brown spotting, and a little blood, but then this morning the 22nd i didn’t have anything. as the day went on i had bad cramps, and then started bleeding again at about 12 pm at school. and then it stopped again. why does it keep starting and stopping? am i on it or not? it keeps stopping and coming but i was supposed to be on it wednesday night. please help. i took a test and it was negative. my period is always regular.