I had sex 15 days after my period and the condom broke?

It is best to take it within 3 days of the exposure but it still may work. It isnt as reliable as regular routine birth control though. Have you thought about getting onto the Pill or another form of hormonal birth control? If you are going to be sexually active and dont want pregnancy, this is your safest bet. See your gynecologist (you should see one at least yearly once you lose your virginity) or see someone at your local family planning clinic for lower cost options if you are a student or low income or no insurance.

Ovulation occurs @ 14 day at the secretory phase of the menstrual cycle. When oocyte(female egg) is release, it's viable for a maximum of 48 to 72 hours. Usually sex from the 12th to 17th day of the cycle has a stronger chance of impregnating the female. Thus on conditions such as release of adequate and viable sperm cells, no hormonal disturbance, viable oocyte etc
But the chances of pregnancy can be prevented with some oral contraceptives. Thus after unprotected sex at the proliferative and secretory phases. For Further clarification u can contact me...