Confused?

Ladies I need some insight before I venture of to the Doctor or Google lol I have a period total of 6 days. Days 1-3 are heavy to medium flow. Days 4-6 are light. Been this way my whole life of periods. Well this period has been so different. I started out with some cramps no biggie then my period. Okay.. Nothing new. UNTIL the next day I could use the restroom either way it hurt so bad and couldnt sit directly on my butt. I'm on day 3 of my period and almost nothing has been on bled since I started bleeding. I took a pregnancy test (cheap... Like 88 cents cheap) and it said negative.