Pregnant?

So I had unprotected sex when eve said my chance of pregnancy was 33%. I'm on birth control, I've been on it for more than a year. He finished on me. On Saturday I had 2 beers and they affected me later on at night, I threw up twice. So I thought maybe the beers messed up my stomach. According to eve my new period starts today & I haven't gotten any symptoms that my period is coming soon. I usually cramp a few days before but I don't feel anything. Could I be pregnant? Or what's going on?