Had unprotected sex on the last day of my period (dec 10) late at night(so early dec 11). took plan b 12 hours later, but have a bmi of 31. my ovulation day is dec 17 and my cycle usually lasts 26 days. what are the chances of being pregnant?

Assume your ovulation day is Dec 17 +/- 2 days, chance of conception is very low (sperms are rarely able to fertilize an egg at 5th day), even if plan B does not work.

Plan B is about 95% effective at preventing pregnancy. Given the timing or your sex, you are at a low risk for pregnancy. If you miss your period by 4-5 days, do a home pregnancy test. If the result is negative repeat the test 4-5 days later unless you get a period by then. Use first morning urine and follow the instructions carefully. Get HPV vaccine. Wish you good health!