Had sex, condom broke. started active birth control that night. took plan b 30 mins after it happened. am i pregnant ?

Unlikely: Unlikely as you took the plan b pill within the 72 hour window. However none of the emergency contraceptives have 100% efficacy so there is still a possibility of getting pregnant but it is low. Hope this helps!

Most likely you are: not. 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. It continues to reduce the risk of pregnancy up to 120 hours (5 days) after unprotected sex, but is less effective as time passes. Take home pregnancy test if period is 7 or more days late.