afraid I'm pregnant

I am a senior in high school and have been extremely stressed due to college applications and last minute ap courses. Me and my boyfriend use condoms and have had no issues that we are aware of and I took plan b mid August (don't know if that could have an effect on my cylce) My period is currently 8 days late, and I'm becoming very paranoid that I am pregnant. Can I be pregnant or is it possible to be delayed from stress?