What Causes Brownish Vaginal Discharge In A Sexually Active Person?

Hi. I have brown, stringy, sometimes lumpy stuff coming out of my vagina. I am not due on my period for another week and after being sexual with my partner twice im the last week this has happened both times straight after. It starts off as a small amount of red blood then goes really brown. The first time i was sexual with my partner last week the browning stopped after a couple of hours. This time it has been happening for 3 days solid and wont stop. I am really worried about this as google has told me numerous things it could be and there is a history of cervical cancer in my family. Do you have any idea why this is happening to me?