Are you often constipated?
Do you have intermittent dull or crampy pain in the left lower abdomen, usually associated with a change in bowel habits?

No to both questions

Your bleeding sounds like diverticular bleeding.
Diverticula are pouches formed along the wall of the large intestine.
When small blood vessels of diverticula's walls are damaged, painless, heavy, dark red beeding can be experienced.
Alcohol can damage the intestinal blood vessels (the injury that causes bleeding is usually chronic one)

Although, this kind of bleeding is not worry some and usually stops by itself, you can ask your doctor for referral for colonoscopy (colonoscopy can revel presence of diverticula, they are frequent appearance in many people, or other gut problems)

However, dark red bleeding can't be due to hemorrhoids.
It can come from your stomach, small intestines or upper part of colon.

Best wishes!
Marija

I have that too, only I don't drink. I can avoid it usually if I don't stimulate myself enough to get an orgasm, but that sorta defeats the purpose. Did you ever find out what it is? It's really annoying.