Help!

Emily • XXVI-X-MMXIII • taurus • good vibes❥
Okay so I have never bleed inbetween periods and my AF isn't due until May 11th but right after my last period I started Microgestin(birth control) and now I'm bleeding and it's like a bright red right at the beginning of my fertile window. is this because of the medicine or should I be worried that something is wrong with me?