What Causes Spotting During Menstruation?

I have had some vaginal spotting for 10 days now. Some days I start the day off with nothing then by afternoon, I have clots and bright red spotting when I wipe. I am 42 years old. Haven't had a regular period in over 10 years and am infertile. I have never had children. One thing that worries me is that I have had at least 80% of the women in my family have had to have emergency hystorectomy's and there have been 3 women who have died from complications stemming from uterine cancer. What do you think is going on?