Had diarrhoea for 10 days noticed i was getting red blood on toilet tissue then bowels returned to normal now noticing thick streaks of red blood in stool every time no hemoroids that i can feel or see just a lot of itching. no pain. what could it be?

If the blood is bright red it means it comes from near the outlet. Often from a crack/fissure in the purse string like closing mechanism of the outlet. The further up the origin the darker red & a shift to purple or black blood would be because of breakdown. Constipation or bulky stools passed quickly can cause such cracks.

This sounds like a rectal/anal fissure (crack in the skin in that area). It is still possible that it is a hemorrhoid as you have itching. Would recommend keeping up with fluids to make your stools less hard if that is the case, applying petroleum jelly or Aquaphor to the area to try to heal any fissure and decrease irritation, and if not improving, please see your doctor.