Headache, Dizziness And Pressure In The Head. Having Blood In Stool. What Is Wrong?

Hi I ve been having problem for years but its minor were I bleed when I empty my bowels, I ve had examinations and a camera recently and all seemed fine this morning I went to empty my bowels and their was a pinky red blood in my stools and a big chunk off bright red either a fully covered stool or clot, it was It was pain free and no pain after the only thing I do have is a constant dull ache on my left side next to my stomach which I thought was my ovaries but scans on that showed all normal I ve also been suffering a lot off headaches and since this morning feel lightheaded a slight feeling of pressure in my head a headache and dizzy , thanks