I had sex around 1-2am today. i took plan b around 2ish the afternoon. my period went off on friday. im at the low fertility window. will it work stil?

Sure, but...: Taking Plan B (or any other emergency contraceptive pill) can alter the timing of the current cycle and of the upcoming cycle. One should check a home urine pregnancy 3 weeks after taking Plan B, to make sure one is not pregnant. Pregnancy tests are sold in stores everywhere. Also, if having sex, one should be sure to use good contraception all the time, so that Plan B is not needed in the future.

Yes: Yes, regardless of where you are in your cycle, Plan B if taken within 72 hours of unprotected or inadequately protected sex will reduce chances of pregnancy dramatically. Considering that you are still in your early cycle (lower chance of conception than the mid-cycle "fertility window,") your risk will just be that much lower. Plan B is likely partially effective even as much as 5 days out.

Plan B: can be used at any time during a woman's menstrual cylce. Timing is important. Plan B One-Step is up to 89 % effective when taken within 72 hours (3 days) after unprotected sex. It can reduce chance of pregnancy by up to 95% if used within 24 hours.