Whats wrong with me?

I had sex without a condom the first time with bae and the second time it was with one, the morning after the second time I woke up and got my period. My period already past about a week ago and I feel like shit. I am very nauseous everyday when I wake up and I can't eat anything at all without wanting to puke. I also took a pregnancy  test to make sure and it was negavtive. What could be going on?