Is This Normal?

okay, this has never really happened to me so i just wanted to know if this had happened to anyone else! so i have been on birth control for a year and a couple of months now. and my period is usually on time. occasionally it would be late. but, yesterday brown stuff (i’m guessing its only blood?) was coming out of me. the thing is, i’m not supposed to be getting my period until 12 days. i was just wondering if it could be my period starting early or something maybe more serious that i need to know. thanks for all the help!!!