Thank you for your query.
Unprotected sex always has a theoretical risk of pregnancy
However since he did not ejaculate, and you also took Plan B
within 24 hours, your chances of pregnancy are pretty remote.
Sometimes, even pre ejaculatory fluid can cause pregnancy though, and emergency pills are 95 % reliable, not 100 % so.
The altered bleeding you mentioned is very common after taking emergency contraceptive
You should wait until you are a week overdue from your expected period, as per your last period date, and then take a pregnancy test, just to be sure.
have safe sex
in the future.