Plan B question

So this might be a dumb question. But I’m going to ask anyway... so me and my fiancé had unprotected sex a couple nights ago and he is pretty sure he didn’t pull out in time. I am due for my period so I’m not ovulating but we decided to get plan B but in case. But I was gonna get it when I went home that night. But then I start to have what looked like period blood and I’m due for my period so I thought it was that but decided to go ahead and take plan B because sometimes my periods are short and I ovulate early. But then the next day I stopped bleeding. And I know it is not implantation bleeding because we haven’t had unprotected sex before that and I just got home from college so I am

Not pregnant. So could the plan B just have messed up my period and will it come for real? I’m supposed to start today and I haven’t