I took the first pill from the birth control pack in the morning and 15 hours later had unprotected sex. what are the chances i may end up pregnant?

Possible: Pregnancy is a possibility in this situation. You should use a second form of birth control during the first month of oral contraception.

Answer: If this is the first time you took birth control pill and your sex date fell around the ovulation date, your chances are very high. If you took the pill to continue from previous months and you've been consistent with it, then your risk is not high. If you had sex out of "dangerous" days, then you may be safe too.

Depends on ur cycle: A healthy woman of reproductive age can become pregnant any time during her cycle, highest chance during/around ovulation and lower during active menstrual flow. It is very difficult to know exactly when ovulation occurs, thus the risk of pregnancy if not using protection. The one pill is not likely making a difference. If u don't want pregnancy, planb (otc) can be used. Consult doc. Good luck.