I had sex 3 weeks ago at 1am and the condom broke right before ejaculation. I took Plan B One Step at about 11am when I woke up. I went to the doctor the next day and found out I had strep throat. I was prescribed medicines and antibiotics a few days later that I began taking. Could the antibiotics have made the Plan B One Step ineffective, even days later? I've been showing really no symptoms of pregnancy besides a little breast tenderness. I'm hoping that along with my appetite increasing is due to my period starting. I still has not come yet and it has me a little worried. Any suggestions?