Some one has advised you all wrong. You are most fertile in your Luteal phase. I hope you know that Luteal phase starts after the ovulation has occurred. Sperms must be deposited in the vagina about 3 days before ovulation and 2 days after ovulation. Those 5 days are most fertile for conceiving. And ovulation occurs 14 days BEFORE NEXT PERIOD. So you should calculate from the expected date of next period (and not from previous periods). For more information please consult with me on Practo.