Plan B causing irregular periods

So I had sex with my guy friend two weeks ago. The next day, he calls me telling me that he feels like we should get Plan B. He wore a condom and pulled out (or at least I think so.) But I agreed to just to be safe. I took the pill 48 hours after having sex, which I know it was still effective at that point. Just not as effective as it would have been within the first 24 hours.

I got HORRIBLE symptoms. Which was expected, considering the extreme dose of hormones I just dumped into my system. I broke out (which is very rare for me), had very sore breasts, fatigue, and was unusually moody.

But the strangest thing was heavy bleeding 12 days before my period was supposed to start.(they’re usually like clockwork) I considered the plan b to be the cause of it and went about my day. But then, it just stopped. Then the next day, I bled some more. Then it just stopped.

I know this sounds insane, but could it be implantation bleeding? Has anyone else experienced this?