Took plan b for the first time (not on bc) 12 hours after unprotected sex (on last day of period). i bled a little 5 days later but have not gotten my period 3 weeks later. my period is 2 days late but pregnancy tests are negative. should i worry?

Pregnancy tests are not that accurate until a week to ten days after a missed period. Retest in about a week.

Conception occurs within day or so of the sex. It takes about 3 weeks for the embryo to make enough HCG for a positive pregnancy test. Blood test may be done a day after a missed period. Home pregnancy tests should be done 4-5 days after the missed period. If the result is negative repeat the test in 4-5 days. Use first morning urine and follow instructions for the test carefully.