Is this a normal thing for periods?

So I started my period in seventh grade and im a sophomore. I have always had four day cycles. I have been sexually active with my long long term boyfriend. He never gets close and I have never been pregnant. My main question is, I got my period or well day one of intense pain where I was crying and wanting to puke and bleeding badly. Then the next day was the same just a little more calm. Then the third day was nothing. Barely anything was there. It was brown with a tint of red and just strange. Now be mindful that for the past two periods my cycle would seem over on the third day and then hit again like it was starting all over. However today would be the fourth day but it's just light bleeding like brown. I was a little curious on why it was two days of intense bleeding and then spotting. Can anyone explain?