longer then usual period

Victoria
Hey ladies, before I call my doctor I wanted to seek advice.
I know this may be silly but, I am usually one of those girls that gets their period on the dot. Meaning if it's due the 1st it will happen around 3 pm on the first. Been like that for years. 
 
Now my last period was 6 days late. I took a test and it came back with a faint line. Wanted to retest later that day. It was a stressful week with work, and loss of a best friend. I figured it was late due to
Stress. 
Later that day when I was going to pick up a new test I got my period. 
Heavy cramps the works. 
Guess it wasn't my turn. 
Now it's been 6 days of terrible cramps and overly heavy flow. Not normal as I'm usually 2 days light/med  1 day heavy 1 day spotting. 
So my question is what could be the reason why period is lasting so long?