I am a 42 year old female. Two weeks before my monthlyperiod, each time I pass stool, I see a lot of blood coming from my vagina. What could be the reason?

See a doctor. Cervicitis, uterine/cervical tumor, fistula, abnormal hormonal cycles are a few of the possibilities. You should be evaluated soon.
See your GYN. And get examined for uterine fibroids, thickening of endometrial lining, cervical polyps, cancer etc. Hopefully there's nothing serious. God bless you! http://m.Everydayhealth.Com/menopause/ menopausal-bleeding.