I've had bright red blood coming from my rectum for a week and have been able to feel my blood pressure dropping at times. what could this be?

G.I. Bleed...: Possibly a medical emergency. Fresh red blood coming from the rectum is always a cause for concern. Hemorrhoids would be a common cause, but other things, such as ulcers, blood vessel malformations, or cancerous lesions should be ruled out--especially given your feeling of "blood pressure drop." This should be evaluated immediately with vital signs, physical exam, possible labs, and other testing.