Sunday night my boyfriend and I were having sex and discovered after that the condom broke. My "fertile window" began today. I have never taken Plan B but read up on it and know that the longest you can wait to take it is 72 hours and that isn't even a 100% guarantee that it will be successful. My question is, tonight will be 72 hours, should I take the Plan B or will I be alright since we had sex on Sunday evening and I'm technically not ovulating until today?