What Causes Cramps Before The Periods Start?

Hi, My last period was June 17 and on July 4or5 I started having cramping like I was on the first day of my cycle. I have been cramping everyday since and on Wednesday night started seeing pink blood through friday and now Saturday I see red blood. By the way, all this time I'm still cramping on and off. What is going on? is it a miscarriage?