Has this happened to anyone else?

So a little over a week ago was the last day of my period, my fiancé and I had unprotected sex and he came in me. Just to be safe I took the plan B pill, then about a week later I started bleeding again, it was about as heavy as my period but only lasted 2 days. I looked it up and the plan B isn't supposed to restart your period it says you should get it as normal. I wasn't sure if it is too heavy to have been implantation bleeding, I took a test but it came out negative. Is it pregnancy and just too early to tell or do you think it was the pill?