Started yaz (drospirenone and ethinyl estradiol) this month, not getting withdrawal bleeding after first cycle of pill. 4 days since last pill. what to do? could antibiotics be reason?

Unlikely: It is not uncommon for young women to miss there period for one or more cycles after starting combined low dose oral contraceptives. With very few exceptions, Antibiotics do not interfere with contraceptive effectiveness or menstrual cycles. However, emotional or physical stress (ie, illness) can alter your menstrual cycle, causing a missed period. Take Care!