Hello,
Thank you for the consult :

The most possible cause for the blood in stool in your case could be hemorrhoids (also know as piles). This can typically cause long standing bloody in stools.

The pain in the left side of your abdomen appears rather non specific. If it is persisting it needed evaluation and an ultrasound scan.

I recommend you to do a blood test -

Hemoglobin levels to see whether you are anemic from the blood loss.

You should fix and appointment with a General Surgeon to confirm the diagnosis of hemorrhoids. You may need further treatment depending on the Surgeon's opinion.

Thank you.