I was the conceiving expert. Just was only lucky enough to bring one of them to full term. Had early miscarriages with several others, much to my heartbreak.

The fertile period is during ovulation, which happens about halfway between each menstrual period. So for a woman who's got an every-28-day menstrual cycle, she generally ovulates in the day 11-13 day range and stays fertilizable for up to a total of 2 1/2 days (so between days 11 and 14 she can get pregnant). For women with regular, predictable periods, the basal body temperature drops two or four points and then quickly spikes upward right after that drop. That's usually a good way to tell when ovulation has begun. The actual release of the ovum into the Fallopian tubes happens about a day and a half before the exact mid-way point of the cycle. Not everyone has even, predictable periods, though. Women can and do ovulate at any time of the month, including when they're having their periods.

I have always been able to clearly tell when I'm ovulating. The urge to be, well, horizontal, is overwhelmingly stronger during that time.