So I do not remember exactly the day i had my last period but I do remember it was ending on the 18th of May. I had sex two weeks later, the 30th of May and I was on birth control and then half way during sex we used a condom. I had sex again on June 4th using the same method, birth control and using a condom half way through sex. I then learned from my doctor that my birth control is less effective because of a different antibiotic I was taking. I then took Plan B in the 72 hour time frame from the second time I had sex just to be safe. So I was supposed to get my period three days ago and I haven't got it. Should I be worried or am I overreacting ?