Period

Okay, so i’m going on week three of my period. after one week it looked like spotting but after a couple days my cramps came back full blown with bright red blood. it’s not enough to soak a bad or tampon but it’s enough to need one. i started birth control on the second of january and i started taking vitamins about 2 weeks ago. i am sexually active. i had a ladies check up on the first of january and o checked out fine. please help. i’m not the kind of person to go to the doctors unless i’m dying. :( but i think i might have too.