What Causes Vaginal Bleeding And Stomach Cramps?

Hi for the past week and a half, i've had very minor spotting after bowel movement and every morning after the first urination - but very minor. I know it is coming from the vagina and I am supposed to get my period right about now. I am not sexually active so I do not know what could be the problem. I having also had some cramping ..... Could this just be my hormones changing or due to possibly the 5 pounds I've gained in the last month?