Headache, Dizzyness, White flashes and bloody stools?

Wow, this sounds like two separate issues. Through my experiences working as a nurse this almost sounds like near fainting as far as your random flashes go. Have you felt like you are going to p out? How about your blood pressure? What has this been running? Also do you get sweaty or feel weak when you have the headaches and dizziness? As far as the rectal blood, this can be due to external or internal hemorrhoids Is the color of the blood bright red and are you saying you see blood in stool or is this on the toilet paper. If I were you get a second opinion from what you GP says. Hope this helps?