Was the first time my period ? Or now? Can I be pregnant?

I had sex on Sunday . & I've bled since Monday . My P tracker on my iPod said my period comes Friday so now I'm wondering if I got my period earlier or if I've been on it this whole week ! The blood simmered down yesterday . But today it's like it started all over again . I dont know what it is & on monday I suffered the biggest cramps of my life ever .