Emergency Contraception: Effectiveness & Timing - Expert Advice

Question
Dear Dr.,

My question is that if me and my partner have sex 3-4 times a day and he ejaculates in me 3-4 times so to prevent pregnancy will i have to take emergency contraceptive pill 3-4 time or only 1 time after having sex 3-4 times a day?
In a month on which day there is a chance of getting pregnant for a girl? On which day she can't get pregnant? Are emergency contraceptive pills effective if he had ejaculated in me?  Please reply me of all my asked questions..specially 1st question about taking pill 3-4 times or 1 time in 72hrs?
Waiting for your reply

Answer
You'd have to take emergency contraception just once for a day when you had sex many times.  I suppose you'd just have to take it once for all the sex you have over 72 hours, although I've never seen a study and am not sure of that.  When a woman can get pregnant depends on how regular her periods are.  If she has regular periods every 28 days, she could possibly get pregnant day 9-15.  However most women aren't perfectly regular, and many things like stress can change their cycle.  Most women can't get pregnant just before, during and after a period, but again, if something changes their cycle, then pregnancy could happen.  Going by calendar days to know when to have sex is one of the least effective methods of birth control.  Emergency contraception is effective if he ejaculated in you.