What Does Dizziness And Nausea After Unprotected Sex Indicate?

HI DOCTORS,
I HAD UNPROTECTED SEX WITH MY PARTNER 3 WEEKS AGO, AND MANY TIMES SINCE, BUT EVEN A FEW DAYS AFTER I STARTED TO FEEL VERY VERY DIZZY AND FEELING SICK EVERYDAY AND SICK COMING UP MY THROAT, EVEN NOW 3 WEEKS LATER. LESS THAN A WEEK AGO I GOT A SLIGHT PERIOD THAT LASTED 1 AND A HALF DAYS, WAS REDDY/BROWN. I HAVEN'T TAKEN A PREGNANCY TEST AS I AM SCARED. MY PERIOD SHOULD BE DUE THIS WEEK BUT NO SIGN AS I USUALLY GET VERY BAD CRAMPS A WEEK BEFORE. PLEASE HELP. THANKS IN ADVANCE.