My partners condom broke on december 28 2015 and i took an emergency pill and now my period is 3days late. should i worry?

Can do a preg. test: Plan B or other emergency contraception pills can alter the menstrual bleeding for the cycle in which the pills were taken, and sometimes the next cycle too. One should be sure to check a home pregnancy test about 3 weeks after sex, to confirm non-pregnancy. Pregnancy is not likely, because emergency pills work most of the time.

Probably not...: If you take the emergency contraceptive pills within the first 24 hours after intercourse, they reduce your risk of pregnancy by up to 95%. If take before 72 hours, they reduce your risk by 88%. That is pretty good, though not perfect. A side effect of taking emergency contraception is frequently a delayed period. If you want to be sure, do a pregnancy test. Best wishes!