Possible Pregnancy Scare: I've Been Given Jolivette Birth Control, I've

Possible Pregnancy Scare: I've been given Jolivette birth control, I've recently been given Ampicillin for a bladder infection. I was sexually active, unprotected Monday of last week, and my period is supposed to come down tomorrow, I usually get cramps the week before it's expected, and that happened. But this morning i had bright red blood when I wiped myself, but then it was gone for the rest of the day. Could I be pregnant, do the pills still work since I'm taking the antibioticor maybe causing a delay with stressing over it?