Having sex with a condom but possibly Precum??

[Makkayaaaa]

Hi, I had sex around The fourth week of October, we had protected sex but I think a little bit of precum, the sex didn’t last very long and within and hour I took plan b. I got my period November 11th and haven’t gotten it since, my normal periods are towards the end of the month, is it normal for periods to be irregular? I’m so stressing out! I heard it delasys them and messes with your schedule.  

[remar]

Plan B can mess with your period. This is not uncommon. You can always take a test to make sure you're not pregnant. I don't think you are because it was only pre semen, which can contain so much less sperm than regular sperm does. And, you took Plan B very fast.