I dont think the blood in the stool is related to the cannabis smoking. However, it is concerning. It may simply be hemorrhoidal bleeding, but that doesn't cause abdominal pain
or nausea. Based on your description of stomach pain and nausea with water, I would also suspect possible gastritis
or peptic ulcers. You can start omeprazole
or any other proton pump
inhibitor medication twice daily for at least two weeks while waiting to see a doctor. If these symptoms continue, I would recommend an upper and lower endoscopy.