Period

I guess I started my period yesterday evening it was brown blood at first then it became red and heavy. But it's goes from light to heavy. I went to the doctor today after taking plan b 3 weeks ago and I wasn't suppose to start until 7 days from now. The doctor did a pregnancy test and it came back negative & he said I have nothing to worry about. But my period just don't seem like any of my other period that I had in the past. Idk I'm probably overthinking it.