I had sex april 3 at 1 am and was uppose to get my period on the 5th but 70 hours after sex i took plan b one step. could plan b one step still work?

Yes: the maximum effectiveness is within 72 hrs but can be moderately effective up to 120 hrs.

Within 72 hours: Plan B decreases the risk of unplanned pregnancy when used within 72 hours of unprotected intercourse. Check a pregnancy test about 2 weeks after use to make sure it worked.

Yes: Levonorgestel-containing emergency contraception like Plan B one step is effective up to five days after unprotected sex, but most effective within first 72hrs - 88% (within 24hrs is best - 92%). Effectiveness is decreased in women > 165lbs, and lost if >175lbs. It also helps that u were due for your period w/i two days of sex. Please see clinician to discuss contraceptive options and start one.