Implantation bleeding or period?

Question to you ladies,

My last period was July 28th through August 2nd. I did have sex during my peak ovulation, however, I started spotting six days before my period. Here comes the dilemma, this spotting has lasted nine days today being the ninth day. It is dark brown in color and will have some pink in it at times lately it's just dark brown. It was never heavy or moderate bleeding. I did have light cramping but nothing compared to how it normally is on my period. Don't know what to think, I want to rule out implantation bleeding but the time in which it started is accurate but the length is not. The spotting has led into when my period would be now. Anyone have any knowledge of this? Thank you